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1
Malgas, Samkelo, Mpho S. Mafa, Brian N. Mathibe e Brett I. Pletschke. "Unraveling Synergism between Various GH Family Xylanases and Debranching Enzymes during Hetero-Xylan Degradation". Molecules 26, n. 22 (9 novembre 2021): 6770. http://dx.doi.org/10.3390/molecules26226770.
Testo completoAbstract (sommario):
Enzymes classified with the same Enzyme Commission (EC) that are allotted in different glycoside hydrolase (GH) families can display different mechanisms of action and substrate specificities. Therefore, the combination of different enzyme classes may not yield synergism during biomass hydrolysis, as the GH family allocation of the enzymes influences their behavior. As a result, it is important to understand which GH family combinations are compatible to gain knowledge on how to efficiently depolymerize biomass into fermentable sugars. We evaluated GH10 (Xyn10D and XT6) and GH11 (XynA and Xyn2A) β-xylanase performance alone and in combination with various GH family α-l-arabinofuranosidases (GH43 AXH-d and GH51 Abf51A) and α-d-glucuronidases (GH4 Agu4B and GH67 AguA) during xylan depolymerization. No synergistic enhancement in reducing sugar, xylose and glucuronic acid released from beechwood xylan was observed when xylanases were supplemented with either one of the glucuronidases, except between Xyn2A and AguA (1.1-fold reducing sugar increase). However, overall sugar release was significantly improved (≥1.1-fold reducing sugar increase) when xylanases were supplemented with either one of the arabinofuranosidases during wheat arabinoxylan degradation. Synergism appeared to result from the xylanases liberating xylo-oligomers, which are the preferred substrates of the terminal arabinofuranosyl-substituent debranching enzyme, Abf51A, allowing the exolytic β-xylosidase, SXA, to have access to the generated unbranched xylo-oligomers. Here, it was shown that arabinofuranosidases are key enzymes in the efficient saccharification of hetero-xylan into xylose. This study demonstrated that consideration of GH family affiliations of the carbohydrate-active enzymes (CAZymes) used to formulate synergistic enzyme cocktails is crucial for achieving efficient biomass saccharification.
2
Vucinic, Jelena, Gleb Novikov, Cédric Montanier, Claire Dumon, Thomas Schiex e Sophie Barbe. "A Comparative Study to Decipher the Structural and Dynamics Determinants Underlying the Activity and Thermal Stability of GH-11 Xylanases". International Journal of Molecular Sciences 22, n. 11 (31 maggio 2021): 5961. http://dx.doi.org/10.3390/ijms22115961.
Testo completoAbstract (sommario):
With the growing need for renewable sources of energy, the interest for enzymes capable of biomass degradation has been increasing. In this paper, we consider two different xylanases from the GH-11 family: the particularly active GH-11 xylanase from Neocallimastix patriciarum, NpXyn11A, and the hyper-thermostable mutant of the environmentally isolated GH-11 xylanase, EvXyn11TS. Our aim is to identify the molecular determinants underlying the enhanced capacities of these two enzymes to ultimately graft the abilities of one on the other. Molecular dynamics simulations of the respective free-enzymes and enzyme–xylohexaose complexes were carried out at temperatures of 300, 340, and 500 K. An in-depth analysis of these MD simulations showed how differences in dynamics influence the activity and stability of these two enzymes and allowed us to study and understand in greater depth the molecular and structural basis of these two systems. In light of the results presented in this paper, the thumb region and the larger substrate binding cleft of NpXyn11A seem to play a major role on the activity of this enzyme. Its lower thermal stability may instead be caused by the higher flexibility of certain regions located further from the active site. Regions such as the N-ter, the loops located in the fingers region, the palm loop, and the helix loop seem to be less stable than in the hyper-thermostable EvXyn11TS. By identifying molecular regions that are critical for the stability of these enzymes, this study allowed us to identify promising targets for engineering GH-11 xylanases. Eventually, we identify NpXyn11A as the ideal host for grafting the thermostabilizing traits of EvXyn11TS.
3
Angelov, Angel, Christoph Loderer, Susanne Pompei e Wolfgang Liebl. "Novel Family of Carbohydrate-Binding Modules Revealed by the Genome Sequence of Spirochaeta thermophila DSM 6192". Applied and Environmental Microbiology 77, n. 15 (17 giugno 2011): 5483–89. http://dx.doi.org/10.1128/aem.00523-11.
Testo completoAbstract (sommario):
ABSTRACTSpirochaeta thermophilais a thermophilic, free-living, and cellulolytic anaerobe. The genome sequence data for this organism have revealed a high density of genes encoding enzymes from more than 30 glycoside hydrolase (GH) families and a noncellulosomal enzyme system for (hemi)cellulose degradation. Functional screening of a fosmid library whose inserts were mapped on theS. thermophilagenome sequence allowed the functional annotation of numerous GH open reading frames (ORFs). Seven different GH ORFs from theS. thermophilaDSM 6192 genome, all putative β-glycanase ORFs according to sequence similarity analysis, contained a highly conserved novel GH-associated module of unknown function at their C terminus. Four of these GH enzymes were experimentally verified as xylanase, β-glucanase, β-glucanase/carboxymethylcellulase (CMCase), and CMCase. Binding experiments performed with the recombinantly expressed and purified GH-associated module showed that it represents a new carbohydrate-binding module (CBM) that binds to microcrystalline cellulose and is highly specific for this substrate. In the course of this work, the new CBM type was only detected inSpirochaeta, but recently we found sequences with detectable similarity to the module in the draft genomes ofCytophaga fermentansandMahella australiensis, both of which are phylogenetically very distant fromS. thermophilaand noncellulolytic, yet inhabit similar environments. This suggests a possibly broad distribution of the module in nature.
4
Iakiviak, Michael, Roderick I. Mackie e Isaac K. O. Cann. "Functional Analyses of Multiple Lichenin-Degrading Enzymes from the Rumen Bacterium Ruminococcus albus 8". Applied and Environmental Microbiology 77, n. 21 (2 settembre 2011): 7541–50. http://dx.doi.org/10.1128/aem.06088-11.
Testo completoAbstract (sommario):
ABSTRACTRuminococcus albus8 is a fibrolytic ruminal bacterium capable of utilization of various plant cell wall polysaccharides. A bioinformatic analysis of a partial genome sequence ofR. albusrevealed several putative enzymes likely to hydrolyze glucans, including lichenin, a mixed-linkage polysaccharide of glucose linked together in β-1,3 and β-1,4 glycosidic bonds. In the present study, we demonstrate the capacity of four glycoside hydrolases (GHs), derived fromR. albus, to hydrolyze lichenin. Two of the genes encoded GH family 5 enzymes (Ra0453 and Ra2830), one gene encoded a GH family 16 enzyme (Ra0505), and the last gene encoded a GH family 3 enzyme (Ra1595). Each gene was expressed inEscherichia coli, and the recombinant protein was purified to near homogeneity. Upon screening on a wide range of substrates, Ra0453, Ra2830, and Ra0505 displayed different hydrolytic properties, as they released unique product profiles. The Ra1595 protein, predicted to function as a β-glucosidase, preferred cleavage of a nonreducing end glucose when linked by a β-1,3 glycosidic bond to the next glucose residue. The major product of Ra0505 hydrolysis of lichenin was predicted to be a glucotriose that was degraded only by Ra0453 to glucose and cellobiose. Most importantly, the four enzymes functioned synergistically to hydrolyze lichenin to glucose, cellobiose, and cellotriose. This lichenin-degrading enzyme mix should be of utility as an additive to feeds administered to monogastric animals, especially those high in fiber.
5
Abe, Koichi, Masahiro Nakajima, Tetsuro Yamashita, Hiroki Matsunaga, Shinji Kamisuki, Takanori Nihira, Yuta Takahashi et al. "Biochemical and structural analyses of a bacterial endo-β-1,2-glucanase reveal a new glycoside hydrolase family". Journal of Biological Chemistry 292, n. 18 (7 marzo 2017): 7487–506. http://dx.doi.org/10.1074/jbc.m116.762724.
Testo completoAbstract (sommario):
β-1,2-Glucan is an extracellular cyclic or linear polysaccharide from Gram-negative bacteria, with important roles in infection and symbiosis. Despite β-1,2-glucan's importance in bacterial persistence and pathogenesis, only a few reports exist on enzymes acting on both cyclic and linear β-1,2-glucan. To this end, we purified an endo-β-1,2-glucanase to homogeneity from cell extracts of the environmental species Chitinophaga arvensicola, and an endo-β-1,2-glucanase candidate gene (Cpin_6279) was cloned from the related species Chitinophaga pinensis. The Cpin_6279 protein specifically hydrolyzed linear β-1,2-glucan with polymerization degrees of ≥5 and a cyclic counterpart, indicating that Cpin_6279 is an endo-β-1,2-glucananase. Stereochemical analysis demonstrated that the Cpin_6279-catalyzed reaction proceeds via an inverting mechanism. Cpin_6279 exhibited no significant sequence similarity with known glycoside hydrolases (GHs), and thus the enzyme defines a novel GH family, GH144. The crystal structures of the ligand-free and complex forms of Cpin_6279 with glucose (Glc) and sophorotriose (Glc-β-1,2-Glc-β-1,2-Glc) determined up to 1.7 Å revealed that it has a large cavity appropriate for polysaccharide degradation and adopts an (α/α)6-fold slightly similar to that of GH family 15 and 8 enzymes. Mutational analysis indicated that some of the highly conserved acidic residues in the active site are important for catalysis, and the Cpin_6279 active-site architecture provided insights into the substrate recognition by the enzyme. The biochemical characterization and crystal structure of this novel GH may enable discovery of other β-1,2-glucanases and represent a critical advance toward elucidating structure-function relationships of GH enzymes.
6
Christensen, Stefan Jarl, Silke Flindt Badino, Ana Mafalda Cavaleiro, Kim Borch e Peter Westh. "Functional analysis of chimeric TrCel6A enzymes with different carbohydrate binding modules". Protein Engineering, Design and Selection 32, n. 9 (settembre 2019): 401–9. http://dx.doi.org/10.1093/protein/gzaa003.
Testo completoAbstract (sommario):
Abstract The glycoside hydrolase (GH) family 6 is an important group of enzymes that constitute an essential part of industrial enzyme cocktails used to convert lignocellulose into fermentable sugars. In nature, enzymes from this family often have a carbohydrate binding module (CBM) from the CBM family 1. These modules are known to promote adsorption to the cellulose surface and influence enzymatic activity. Here, we have investigated the functional diversity of CBMs found within the GH6 family. This was done by constructing five chimeric enzymes based on the model enzyme, TrCel6A, from the soft-rot fungus Trichoderma reesei. The natural CBM of this enzyme was exchanged with CBMs from other GH6 enzymes originating from different cellulose degrading fungi. The chimeric enzymes were expressed in the same host and investigated in adsorption and quasi-steady-state kinetic experiments. Our results quantified functional differences of these phylogenetically distant binding modules. Thus, the partitioning coefficient for substrate binding varied 4-fold, while the maximal turnover (kcat) showed a 2-fold difference. The wild-type enzyme showed the highest cellulose affinity on all tested substrates and the highest catalytic turnover. The CBM from Serendipita indica strongly promoted the enzyme’s ability to form productive complexes with sites on the substrate surface but showed lower turnover of the complex. We conclude that the CBM plays an important role for the functional differences between GH6 wild-type enzymes.
7
Ramirez, María Cecilia, Guillermina María Luque, Ana María Ornstein e Damasia Becu-Villalobos. "Differential neonatal testosterone imprinting of GH-dependent liver proteins and genes in female mice". Journal of Endocrinology 207, n. 3 (13 ottobre 2010): 301–8. http://dx.doi.org/10.1677/joe-10-0276.
Testo completoAbstract (sommario):
Abnormal exposure to steroid hormones within a critical developmental period elicits permanent alterations in female reproductive physiology in rodents, but the impact on the female GH axis and the underlying sexual differences in hepatic enzymes have not been described in detail. We have investigated the effect of neonatal androgenization of female mice (achieved by s.c. injection of 100 μg testosterone propionate (TP) on the day of birth: TP females) on the GHRH–somatostatin–GH axis and downstream GH targets, which included female and male predominant liver enzymes and secreted proteins. At 4 months of age, an organizational effect of neonatal testosterone was evidenced on hypothalamic Ghrh mRNA level but not on somatostatin (stt) mRNA level. Ghrh mRNA levels were higher in males than in females, but not in TP females. Increased expression in TP females correlated with increased pituitary GH content and somatotrope population, increased serum and liver IGF-I concentration, and ultimately higher body weight. Murine urinary proteins (MUPs) that were excreted at higher levels in male urine, and whose expression requires pulsatile occupancy of liver GH receptors, were not modified in TP females and neither was liver Mup 1/2/6/8 mRNA expression. Furthermore, a male predominant liver gene (Cyp2d9) was not masculinized in TP females either, whereas two female predominant genes (Cyp2b9 and Cyp2a4) were defeminized. These data support the hypothesis that neonatal steroid exposure contributes to the remodeling of the GH axis and defeminization of hepatic steroid-metabolizing enzymes, which may compromise liver physiology.
8
Grøfte, Thorbjørn, Dorthe Svenstrup Jensen, Henning Grønbæk, Troels Wolthers, Søren Astrup Jensen, Niels Tygstrup e Hendrik Vilstrup. "Effects of growth hormone on steroid-induced increase in ability of urea synthesis and urea enzyme mRNA levels". American Journal of Physiology-Endocrinology and Metabolism 275, n. 1 (1 luglio 1998): E79—E86. http://dx.doi.org/10.1152/ajpendo.1998.275.1.e79.
Testo completoAbstract (sommario):
Growth hormone (GH) reduces the catabolic side effects of steroid treatment due to its effects on tissue protein synthesis/degradation. Little attention is focused on hepatic amino acid degradation and urea synthesis. Five groups of rats were given 1) placebo, 2) prednisolone, 3) placebo, pair fed to the steroid group, 4) GH, and 5) prednisolone and GH. After 7 days, the in vivo capacity of urea N synthesis (CUNS) was determined by saturating alanine infusion, in parallel with measurements of liver mRNA levels of urea cycle enzymes, N contents of organs, N balance, and hormones. Prednisolone increased CUNS (μmol ⋅ min−1 ⋅ 100 g−1, mean ± SE) from 9.1 ± 1.0 (pair-fed controls) to 13.2 ± 0.8 ( P < 0.05), decreased basal blood α-amino N concentration from 4.2 ± 0.5 to 3.1 ± 0.3 mmol/l ( P < 0.05), increased mRNA levels of the rate- and flux-limiting urea cycle enzymes by 20 and 65%, respectively ( P < 0.05), and decreased muscle N contents and N balance. In contrast, GH decreased CUNS from 6.1 ± 0.9 (free-fed controls) to 4.2 ± 0.5 ( P < 0.05), decreased basal blood α-amino N concentration from 3.8 ± 0.3 to 3.2 ± 0.2, decreased mRNA levels of the rate- and flux-limiting urea cycle enzymes to 60 and 40%, respectively ( P < 0.05), and increased organ N contents and N balance. Coadministration of GH abolished all steroid effects. We found that prednisolone increases the ability of amino N conversion into urea N and urea cycle gene expression. GH had the opposite effects and counteracted the N-wasting side effects of prednisolone.
9
Janeček, Štefan, e Birte Svensson. "How many α-amylase GH families are there in the CAZy database?" Amylase 6, n. 1 (1 gennaio 2022): 1–10. http://dx.doi.org/10.1515/amylase-2022-0001.
Testo completoAbstract (sommario):
Abstract The CAZy database is a web-server for sequence-based classification of carbohydrate-active enzymes that has become the worldwide and indispensable tool for scientists engaged in this research field. It was originally created in 1991 as a classification of glycoside hydrolases (GH) and currently, this section of CAZy represents its largest part counting 172 GH families. The present Opinion paper is devoted to the specificity of α-amylase (EC 3.2.1.1) and its occurrence in the CAZy database. Among the 172 defined GH families, four, i.e. GH13, GH57, GH119 and GH126, may be considered as the α-amylase GH families. This view reflects a historical background and traditions widely accepted during the previous decades with respect to the chronology of creating the individual GH families. It obeys the phenomenon that some amylolytic enzymes, which were used to create the individual GH families and were originally known as α-amylases, according to current knowledge from later, more detailed characterization, need not necessarily represent genuine α-amylases. Our Opinion paper was therefore written in an effort to invite the scientific community to think about that with a mind open to changes and to consider the seemingly unambiguous question in the title as one that may not have a simple answer.
10
Olsson, Bob, Mohammad Bohlooly-Y, Ola Brusehed, Olle G. P. Isaksson, Bo Ahrén, Sven-Olof Olofsson, Jan Oscarsson e Jan Törnell. "Bovine growth hormone-transgenic mice have major alterations in hepatic expression of metabolic genes". American Journal of Physiology-Endocrinology and Metabolism 285, n. 3 (settembre 2003): E504—E511. http://dx.doi.org/10.1152/ajpendo.00444.2002.
Testo completoAbstract (sommario):
Transgenic mice overexpressing growth hormone (GH) have been extensively used to study the chronic effects of elevated serum levels of GH. GH is known to have many acute effects in the liver, but little is known about the chronic effects of GH overexpression on hepatic gene expression. Therefore, we used DNA microarray to compare gene expression in livers from bovine GH (bGH)-transgenic mice and littermates. Hepatic expression of peroxisome proliferator-activated receptor-α (PPARα) and genes involved in fatty acid activation, peroxisomal and mitochondrial β-oxidation, and production of ketone bodies was decreased. In line with this expression profile, bGH-transgenic mice had a reduced ability to form ketone bodies in both the fed and fasted states. Although the bGH mice were hyperinsulinemic, the expression of sterol regulatory element-binding protein (SREBP)-1 and most lipogenic enzymes regulated by SREBP-1 was reduced, indicating that these mice are different from other insulin-resistant models with respect to expression of SREBP-1 and its downstream genes. This study also provides several candidate genes for the well-known association between elevated GH levels and cardiovascular disease, e.g., decreased expression of scavenger receptor class B type I, hepatic lipase, and serum paraoxonase and increased expression of serum amyloid A-3 protein. We conclude that bGH-transgenic mice display marked changes in hepatic genes coding for metabolic enzymes and suggest that GH directly or indirectly regulates many of these hepatic genes via decreased expression of PPARα and SREBP-1.
11
Kawai, Masahiko, Stelvio M. Bandiera, Thomas KH Chang e Gail D. Bellward. "Effect of exogenous growth hormone on somatic growth, gonadal development, and hepatic CYP2C11 and CYP2C12 expression in prepubertal intact male rats". Canadian Journal of Physiology and Pharmacology 79, n. 4 (1 aprile 2001): 352–61. http://dx.doi.org/10.1139/y00-128.
Testo completoAbstract (sommario):
The influence of exogenous growth hormone (GH) on pubertal maturation, as assessed by growth, age of preputial separation, testicular development, and hepatic expression of sexually dimorphic cytochrome P450 (CYP) enzymes, was investigated. Treatment of 22-day old prepubertal intact male rats with twice daily subcutaneous (sc) injections of rat recombinant GH (0.12 µg/g body weight) for 12 or 21 days did not affect body weight, skeletal growth, or testicular weight. By comparison, GH suppressed hepatic CYP2C11 enzyme activity, protein, and mRNA levels but induced CYP2C12 expression. GH suppressed CYP2C11 expression by approximately 60% in prepubertal rats as compared with 30% in adult rats, whereas it increased CYP2C12 levels to 80% of the normal female levels but had no effect in adult male rats. Twice daily intravenous injections of GH suppressed CYP2C11 only. Increasing the sc dose of GH 30-fold produced little or no additional change in CYP2C11 or CYP2C12 expression, whereas it modestly increased body weight and skeletal growth and reduced testicular weight. Overall, the present study provides the first demonstration that prepubertal administration (22-33 days of age) of GH at a pharmacologically relevant dose (0.12 µg/g twice daily) suppressed hepatic expression of CYP2C11 in 34-day-old intact male rats, suggesting that in this age group the liver is intrinsically responsive to transcription factors involved in the regulation of GH-dependent, sex-specific CYP gene expression. A higher dose (3.6 µg/g) of GH administered during the prepubertal period was required to elicit a modest effect on somatic growth and gonadal development.Key words: cytochrome P450, CYP2C11, CYP2C12, growth hormone, preputial separation, pubertal development, testosterone.
12
Argetsinger, L. S., e C. Carter-Su. "Mechanism of signaling by growth hormone receptor". Physiological Reviews 76, n. 4 (1 ottobre 1996): 1089–107. http://dx.doi.org/10.1152/physrev.1996.76.4.1089.
Testo completoAbstract (sommario):
Growth hormone (GH) has long been known to stimulate linear growth and regulate metabolism. The cellular mechanism by which GH elicits these effects has only recently begun to be understood. This review provides an overview of a current model of GH signaling. Briefly, binding of GH to GH receptor induces receptor dimerization and activation of the tyrosine kinase JAK2. Tyrosyl phosphorylation of GH receptor and JAK2 recruits and activates signaling molecules such as Stat transcription factors, SHC, and insulin receptor substrates 1 and 2 that lead to the release of second messengers such as diacylglycerol, calcium, and nitric oxide and the activation of enzymes such as mitogen-activated protein kinase, protein kinase C, phospholipase A2, and phosphatidylinositol 3'-kinase. These pathways regulate cellular function including gene transcription, metabolite transport, and enzymatic activity that result in the ability of GH to control body growth and metabolism.
13
Radzlin, Nurfatini, Amira Suriaty Yaakop, Kian Mau Goh, Kok Jun Liew, Iffah Izzati Zakaria e Ummirul Mukminin Kahar. "Genome Analysis of Celeribacter sp. PS-C1 Isolated from Sekinchan Beach in Selangor, Malaysia, Reveals Its β-Glucosidase and Licheninase Activities". Microorganisms 10, n. 2 (10 febbraio 2022): 410. http://dx.doi.org/10.3390/microorganisms10020410.
Testo completoAbstract (sommario):
A halophilic marine bacterial strain, PS-C1, was isolated from Sekinchan beach in Selangor, Malaysia. The 16S rRNA gene sequence analysis indicated that strain PS-C1 was associated with the genus Celeribacter. To date, there have been no reports on enzymes from the genus Celeribacter. The present study reports on the cellular features of Celeribacter sp. PS-C1, its annotated genome sequence, and comparative genome analyses of Celeribacter glycoside hydrolase (GH) enzymes. The genome of strain PS-C1 has a size of 3.87 Mbp and a G+C content of 59.10%, and contains 3739 protein-coding genes. Detailed analysis using the Carbohydrate-Active enZYmes (CAZy) database revealed that Celeribacter genomes harboured at least 12 putative genes encoding industrially important GHs that are grouped as cellulases, β-glucanases, hemicellulases, and starch-degrading enzymes. Herein, the potential applications of these enzymes are discussed. Furthermore, the activities of two types of GHs (β-glucosidase and licheninase) in strain PS-C1 were demonstrated. These findings suggest that strain PS-C1 could be a reservoir of novel GH enzymes for lignocellulosic biomass degradation.
14
Hüttner, A., E. F. Adams, M. Buchfelder e R. Fahlbusch. "Growth hormone gene structure in human pituitary somatotrophinomas: promoter region sequence and methylation studies". Journal of Molecular Endocrinology 12, n. 2 (aprile 1994): 167–72. http://dx.doi.org/10.1677/jme.0.0120167.
Testo completoAbstract (sommario):
ABSTRACT The structure of the GH gene in human somatotrophinomas was examined in terms of promoter region sequence and degree of methylation. In six tumours, the promoter sequence did not differ from that observed in the corresponding genomic (white blood cell-derived) DNA, suggesting that it is unlikely that excessive GH production is due to a point mutation within this region. In contrast, Southern blot analysis using the methylation-sensitive restriction enzymes HpaII and HhaI revealed lower levels of methylation of the GH gene in somatotrophinomas when compared with that found in DNA derived from normal pituitary glands. We conclude that hypomethylation of the GH gene in human somatotrophinomas may play at least a partial role in excessive GH production.
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Wan, Qun, Jerry M. Parks, B. Leif Hanson, Suzanne Zoe Fisher, Andreas Ostermann, Tobias E. Schrader, David E. Graham, Leighton Coates, Paul Langan e Andrey Kovalevsky. "Direct determination of protonation states and visualization of hydrogen bonding in a glycoside hydrolase with neutron crystallography". Proceedings of the National Academy of Sciences 112, n. 40 (21 settembre 2015): 12384–89. http://dx.doi.org/10.1073/pnas.1504986112.
Testo completoAbstract (sommario):
Glycoside hydrolase (GH) enzymes apply acid/base chemistry to catalyze the decomposition of complex carbohydrates. These ubiquitous enzymes accept protons from solvent and donate them to substrates at close to neutral pH by modulating the pKa values of key side chains during catalysis. However, it is not known how the catalytic acid residue acquires a proton and transfers it efficiently to the substrate. To better understand GH chemistry, we used macromolecular neutron crystallography to directly determine protonation and ionization states of the active site residues of a family 11 GH at multiple pD (pD = pH + 0.4) values. The general acid glutamate (Glu) cycles between two conformations, upward and downward, but is protonated only in the downward orientation. We performed continuum electrostatics calculations to estimate the pKa values of the catalytic Glu residues in both the apo- and substrate-bound states of the enzyme. The calculated pKa of the Glu increases substantially when the side chain moves down. The energy barrier required to rotate the catalytic Glu residue back to the upward conformation, where it can protonate the glycosidic oxygen of the substrate, is 4.3 kcal/mol according to free energy simulations. These findings shed light on the initial stage of the glycoside hydrolysis reaction in which molecular motion enables the general acid catalyst to obtain a proton from the bulk solvent and deliver it to the glycosidic oxygen.
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Ljungmann, K., T. Grøfte, P. Kissmeyer-Nielsen, A. Flyvbjerg, H. Vilstrup, N. Tygstrup e S. Laurberg. "GH decreases hepatic amino acid degradation after small bowel resection in rats without enhancing bowel adaptation". American Journal of Physiology-Gastrointestinal and Liver Physiology 279, n. 4 (1 ottobre 2000): G700—G706. http://dx.doi.org/10.1152/ajpgi.2000.279.4.g700.
Testo completoAbstract (sommario):
Growth hormone (GH) treatment in short bowel syndrome is controversial, and the mechanisms of a possible positive effect remain to be elucidated. Rats were randomly subjected to either an 80% jejunoileal resection or sham operation and were given either placebo (NaCl) or biosynthetic rat GH (brGH). The in vivo capacity of urea nitrogen synthesis (CUNS) and the expression of urea cycle enzymes were measured and related to changes in body weight and adaptive growth in ileal segments on days 7and 14. Ileal segments were examined by unbiased stereological techniques. brGH treatment decreased CUNS among the resected rats by 19% ( P < 0.05) and 36% ( P < 0.05) on days 7 and 14, respectively. The mRNA levels of urea cycle enzyme genes were not influenced by brGH treatment. brGH treatment did not increase the adaptive growth in the ileal segments. In conclusion, we found that GH treatment decreased the accelerated postoperative hepatic amino acid degradation in experimental short bowel syndrome without enhancing the morphological intestinal adaptation.
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Das, Rajat K., Sarmistha Banerjee e Bernard H. Shapiro. "Growth hormone: a newly identified developmental organizer". Journal of Endocrinology 232, n. 3 (marzo 2017): 377–89. http://dx.doi.org/10.1530/joe-16-0471.
Testo completoAbstract (sommario):
The sexually dimorphic expression of cytochromes P450 (CYP) drug-metabolizing enzymes has been reported in all species examined. These sex differences are only expressed during adulthood and are solely regulated by sex differences in circulating growth hormone (GH) profiles. Once established, however, the different male- and female-dependent CYP isoform profiles are permanent and immutable, suggesting that adult CYP expression requires imprinting. As the hormone that regulates an adult function is likely the same hormone that imprints the function, we selectively blocked GH secretion in some newborn male rats, whereas others received concurrent physiologic replacement of rat GH. The results demonstrate that adult male GH activation of the signal transduction pathway regulating expression of the principal CYP2C11 isoform is obligatorily dependent on perinatal GH imprinting, without which CYP2C11 and drug metabolism would be permanently and profoundly suppressed. As there are other adult metabolic functions also regulated by GH, pediatric drug therapy known to disrupt GH secretion could unintentionally impair adult health.
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Galanopoulou, Anastasia P., Irini Haimala, Daphne N. Georgiadou, Diomi Mamma e Dimitris G. Hatzinikolaou. "Characterization of the Highly Efficient Acid-Stable Xylanase and β-Xylosidase System from the Fungus Byssochlamys spectabilis ATHUM 8891 (Paecilomyces variotii ATHUM 8891)". Journal of Fungi 7, n. 6 (29 maggio 2021): 430. http://dx.doi.org/10.3390/jof7060430.
Testo completoAbstract (sommario):
Two novel xylanolytic enzymes, a xylanase and a β-xylosidase, were simultaneously isolated and characterized from the extracellular medium of Byssochlamys spectabilis ATHUM 8891 (anamorph Paecilomyces variotii ATHUM 8891), grown on Brewer’s Spent Grain as a sole carbon source. They represent the first pair of characterized xylanolytic enzymes of the genus Byssochlamys and the first extensively characterized xylanolytic enzymes of the family Thermoascaceae. In contrast to other xylanolytic enzymes isolated from the same family, both enzymes are characterized by exceptional thermostability and stability at low pH values, in addition to activity optima at temperatures around 65 °C and acidic pH values. Applying nano-LC-ESI-MS/MS analysis of the purified SDS-PAGE bands, we sequenced fragments of both proteins. Based on sequence-comparison methods, both proteins appeared conserved within the genus Byssochlamys. Xylanase was classified within Glycoside Hydrolase family 11 (GH 11), while β-xylosidase in Glycoside Hydrolase family 3 (GH 3). The two enzymes showed a synergistic action against xylan by rapidly transforming almost 40% of birchwood xylan to xylose. The biochemical profile of both enzymes renders them an efficient set of biocatalysts for the hydrolysis of xylan in demanding biorefinery applications.
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Pellizas, Claudia G., Aldo H. Coleoni, Ana M. Cabanillas, Ana M. Masini-Repiso e María E. Costamagna. "Response of triiodothyronine-dependent enzyme activities to insulin-like growth factor I and growth hormone in cultured rat hepatocytes". European Journal of Endocrinology 134, n. 2 (febbraio 1996): 215–20. http://dx.doi.org/10.1530/eje.0.1340215.
Testo completoAbstract (sommario):
Pellizas CG, Coleoni AH, Cabanillas AM, Masini-Repiso AM, Costamagna ME. Response of triiodothyronine-dependent enzyme activities to insulin-like growth factor I and growth hormone in cultured cat hepatocytes. Eur J Endocrinol 1996:134:215–20. ISSN 0804–4643 Triiodothyronine (T3) is involved in the regulation of the growth hormone-insulin-like growth factor I (GH-IGF-I) axis. In this study we investigated the effect of GH and IGF-I on the metabolic response of T3 in target tissues by evaluating the activity of two T3-dependent liver enzymes: mitochondrial α-glycerophosphate dehydrogenase (α-GPD) and cytosolic malic enzyme (ME) in rat hepatocytes in primary culture. Growth hormone (35 nmol/l) as well as IGF-I (0.5 μmol/l) reduced α-GPD and ME activities (p < 0.01) compared to the control group. Timecourse studies indicated that IGF-I 1.5 μmol/l) significantly decreased α-GPD and ME activities (p < 0.01) after 24 h, whereas the effect of GH (35 nmol/l) was recorded only after 36 h (p < 0.01). This delayed effect of GH compared to IGF-I suggested the possibility that the effect of GH could be mediated by IGF-I synthesis. To test this hypothesis, the effect of GH on the two enzyme activities was studied in the presence of anti-IGF-I antibodies. A gradual recovery of α-GPD and ME activities (p < 0.01) was observed in the presence of GH (35 nmol/l) plus increasing concentrations of anti-IGF-I antiserum. The maximal α-GPD and ME activities attained after the incubation of the liver cells with 1 μmol/l T3. a concentration high enough to fully saturate the nuclear T3 receptors for 24 h, were lowered significantly by 1.0 μmol/l IGF-I (p < 0.01). This finding suggests that the IGF-I effect might be independent of the saturation of the nuclear T3 receptors. In conclusion, in cultured rat hepatocytes, GH and IGF-I reduced the metabolic response of T3 evaluated by two liver T3-dependent enzyme activities. The effect of GH was mediated at least in part by IGF-I. Claudia G Pellizas, Dpto Bioquímica Clínica, Facultad de Ciencias Químicas, Universidad Nacional de Códoba, Casilla de Correo 61, Sucursal 16, (5016) Córdoba, Argentina.
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Li, Xinna, Andrzej Bartke, Darlene E. Berryman, Kevin Funk, John J. Kopchick, Edward O. List, Liou Sun e Richard A. Miller. "Direct and indirect effects of growth hormone receptor ablation on liver expression of xenobiotic metabolizing genes". American Journal of Physiology-Endocrinology and Metabolism 305, n. 8 (15 ottobre 2013): E942—E950. http://dx.doi.org/10.1152/ajpendo.00304.2013.
Testo completoAbstract (sommario):
Detoxification of ingested xenobiotic chemicals, and of potentially toxic endogenous metabolites, is carried out largely through a series of enzymes synthesized in the liver, sometimes called “xenobiotic metabolizing enzymes” (XME). Expression of these XME is sexually dimorphic in rodents and humans, with many of the XME expressed at higher levels in females. This expression pattern is thought to be regulated, in part, by the sex differences in circadian growth hormone (GH) pulsatility. We have evaluated mRNA, in the liver, for 52 XME genes in male and female mice of four mutant stocks, with diminished levels of GH receptor (GHR) either globally (GKO), or in liver (LKO), fat (FKO), or muscle (MKO) tissue specifically. The data show complex, sex-specific changes. For some XME, the expression pattern is consistent with direct control of hepatic mRNA by GHR in the liver. In contrast, other XME show evidence for indirect pathways in which hepatic XME expression is altered by GH signals in fat or skeletal muscle. The effects of GHR-null mutations on glucose control, responses to dietary interventions, steroid metabolism, detoxification pathways, and lifespan may depend on a mixture of direct hepatic effects and cross talk between different GH-responsive tissues.
21
Poria, Vikram, Anuj Rana, Arti Kumari, Jasneet Grewal, Kumar Pranaw e Surender Singh. "Current Perspectives on Chitinolytic Enzymes and Their Agro-Industrial Applications". Biology 10, n. 12 (12 dicembre 2021): 1319. http://dx.doi.org/10.3390/biology10121319.
Testo completoAbstract (sommario):
Chitinases are a large and diversified category of enzymes that break down chitin, the world’s second most prevalent polymer after cellulose. GH18 is the most studied family of chitinases, even though chitinolytic enzymes come from a variety of glycosyl hydrolase (GH) families. Most of the distinct GH families, as well as the unique structural and catalytic features of various chitinolytic enzymes, have been thoroughly explored to demonstrate their use in the development of tailor-made chitinases by protein engineering. Although chitin-degrading enzymes may be found in plants and other organisms, such as arthropods, mollusks, protozoans, and nematodes, microbial chitinases are a promising and sustainable option for industrial production. Despite this, the inducible nature, low titer, high production expenses, and susceptibility to severe environments are barriers to upscaling microbial chitinase production. The goal of this study is to address all of the elements that influence microbial fermentation for chitinase production, as well as the purifying procedures for attaining high-quality yield and purity.
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Hidaka, Masafumi, Yuji Honda, Motomitsu Kitaoka, Satoru Nirasawa, Kiyoshi Hayashi, Takayoshi Wakagi, Hirofumi Shoun e Shinya Fushinobu. "Reaction Mechanism and Substrate Recognition of GH-94 Phosphorolytic Enzymes". Journal of Applied Glycoscience 52, n. 2 (2005): 191–96. http://dx.doi.org/10.5458/jag.52.191.
Testo completo
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Qin, Zhen, Qiaojuan Yan, Jian Lei, Shaoqing Yang, Zhengqiang Jiang e Shiwang Wu. "The first crystal structure of a glycoside hydrolase family 17 β-1,3-glucanosyltransferase displays a unique catalytic cleft". Acta Crystallographica Section D Biological Crystallography 71, n. 8 (31 luglio 2015): 1714–24. http://dx.doi.org/10.1107/s1399004715011037.
Testo completoAbstract (sommario):
β-1,3-Glucanosyltransferase (EC 2.4.1.–) plays an important role in the formation of branched glucans, as well as in cell-wall assembly and rearrangement in fungi and yeasts. The crystal structures of a novel glycoside hydrolase (GH) family 17 β-1,3-glucanosyltransferase fromRhizomucor miehei(RmBgt17A) and the complexes of its active-site mutant (E189A) with two substrates were solved at resolutions of 1.30, 2.30 and 2.27 Å, respectively. The overall structure ofRmBgt17A had the characteristic (β/α)8TIM-barrel fold. The structures ofRmBgt17A and other GH family 17 members were compared: it was found that a conserved subdomain located in the region near helix α6 and part of the catalytic cleft in other GH family 17 members was absent inRmBgt17A. Instead, four amino-acid residues exposed to the surface of the enzyme (Tyr135, Tyr136, Glu158 and His172) were found in the reducing terminus of subsite +2 ofRmBgt17A, hindering access to the catalytic cleft. This distinct region ofRmBgt17A makes its catalytic cleft shorter than those of other reported GH family 17 enzymes. The complex structures also illustrated thatRmBgt17A can only provide subsites −3 to +2. This structural evidence provides a clear explanation of the catalytic mode ofRmBgt17A, in which laminaribiose is released from the reducing end of linear β-1,3-glucan and the remaining glucan is transferred to the end of another β-1,3-glucan acceptor. The first crystal structure of a GH family 17 β-1,3-glucanosyltransferase may be useful in studies of the catalytic mechanism of GH family 17 proteins, and provides a basis for further enzymatic engineering or antifungal drug screening.
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Carvalho, S. D., N. Negrao e A. C. Bianco. "Hormonal regulation of malic enzyme and glucose-6-phosphate dehydrogenase in brown adipose tissue". American Journal of Physiology-Endocrinology and Metabolism 264, n. 6 (1 giugno 1993): E874—E881. http://dx.doi.org/10.1152/ajpendo.1993.264.6.e874.
Testo completoAbstract (sommario):
The activities of malic enzyme (ME) and glucose-6-phosphate dehydrogenase (G-6-PDH), two NADPH-generating lipogenic enzymes, were measured in brown adipose tissue (BAT) of rats undergoing various neurohormonal manipulations. Methimazole-induced hypothyroidism doubled the activity of these two enzymes but, surprisingly, triiodothyronine (T3) given to hypothyroid rats caused a time- and dose-dependent stimulation of up to three- to fourfold. Unilateral BAT denervation modestly reduced the activity of these enzymes (approximately 30%) and failed to prevent the stimulation induced by hypothyroidism, whereas growth hormone (GH) successfully blocked this effect of hypothyroidism. Insulin stimulated both enzymes regardless of the thyroid status but failed to abolish the inhibitory effect of GH. In intact rats, cold exposure caused a time-dependent increase in the activity of both ME and G-6-PDH, which reached 5.2- and 3-fold, respectively, after 96 h. This cold-induced stimulation was not observed in hypothyroid rats, but it was restored by physiological doses of thyroxine (800 ng.100 g body wt-1.24 h-1). Replacement with T3 (300 ng.100 g body wt-1.24 h-1), in contrast, did not have this effect. In hypothyroid rats with hemidenervation of BAT, norepinephrine (NE) modestly increased ME and G-6-PDH activities in the denervated side, with little or no effect in the intact side. Receptor-saturating doses of T3 (50 micrograms.100 g body wt-1.day-1 over 48 h) stimulated two- and threefold both enzymes in both sides, reducing or obliterating the effect of denervation. The data suggest a complex neurohormonal regulation of the activity of ME and G-6-PDH in BAT.(ABSTRACT TRUNCATED AT 250 WORDS)
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Frick, Fredrik, Daniel Lindén, Caroline Améen, Staffan Edén, Agneta Mode e Jan Oscarsson. "Interaction between growth hormone and insulin in the regulation of lipoprotein metabolism in the rat". American Journal of Physiology-Endocrinology and Metabolism 283, n. 5 (1 novembre 2002): E1023—E1031. http://dx.doi.org/10.1152/ajpendo.00260.2002.
Testo completoAbstract (sommario):
The importance of insulin for the in vivo effects of growth hormone (GH) on lipid and lipoprotein metabolism was investigated by examining the effects of GH treatment of hypophysectomized (Hx) female rats with and without concomitant insulin treatment. Hypophysectomy-induced changes of HDL, apolipoprotein (apo)E, LDL, and apoB levels were normalized by GH treatment but not affected by insulin treatment. The hepatic triglyceride secretion rate was lower in Hx rats than in normal rats and increased by GH treatment. This effect of GH was blunted by insulin treatment. The triglyceride content in the liver changed in parallel with the changes in triglyceride secretion rate, indicating that the effect of the hormones on triglyceride secretion was dependent on changed availability of triglycerides for VLDL assembly. GH and insulin independently increased editing of apoB mRNA, but the effects were not additive. The expression of fatty-acid synthase (FAS), stearoyl-CoA desaturase-1 (SCD-1), and sterol regulatory element-binding protein-1c (SREBP-1c) was increased by GH treatment. Insulin and GH had no additive effects on these genes; instead, insulin blunted the effect of GH on SREBP-1c mRNA. In contrast to the liver, adipose tissue expression of SREBP-1c, FAS, or SCD-1 mRNA was not influenced by GH. In conclusion, the increased hepatic expression of lipogenic enzymes after GH treatment may be explained by increased expression of SREBP-1c. Insulin does not mediate the effects of GH but inhibits the stimulatory effect of GH on hepatic SREBP-1c expression and triglyceride secretion rate.
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Munoz-Munoz, Jose, Alan Cartmell, Nicolas Terrapon, Bernard Henrissat e Harry J. Gilbert. "Unusual active site location and catalytic apparatus in a glycoside hydrolase family". Proceedings of the National Academy of Sciences 114, n. 19 (10 aprile 2017): 4936–41. http://dx.doi.org/10.1073/pnas.1701130114.
Testo completoAbstract (sommario):
The human gut microbiota use complex carbohydrates as major nutrients. The requirement for an efficient glycan degrading systems exerts a major selection pressure on this microbial community. Thus, we propose that these bacteria represent a substantial resource for discovering novel carbohydrate active enzymes. To test this hypothesis, we focused on enzymes that hydrolyze rhamnosidic bonds, as cleavage of these linkages is chemically challenging and there is a paucity of information on l-rhamnosidases. Here we screened the activity of enzymes derived from the human gut microbiota bacterium Bacteroides thetaiotaomicron, which are up-regulated in response to rhamnose-containing glycans. We identified an α-l-rhamnosidase, BT3686, which is the founding member of a glycoside hydrolase (GH) family, GH145. In contrast to other rhamnosidases, BT3686 cleaved l-Rha-α1,4–d-GlcA linkages through a retaining double-displacement mechanism. The crystal structure of BT3686 showed that the enzyme displayed a type A seven-bladed β-propeller fold. Mutagenesis and crystallographic studies, including the structure of BT3686 in complex with the reaction product GlcA, revealed a location for the active site among β-propeller enzymes cited on the posterior surface of the rhamnosidase. In contrast to the vast majority of GH, the catalytic apparatus of BT3686 does not comprise a pair of carboxylic acid residues but, uniquely, a single histidine functions as the only discernable catalytic amino acid. Intriguingly, the histidine, His48, is not invariant in GH145; however, when engineered into structural homologs lacking the imidazole residue, α-l-rhamnosidase activity was established. The potential contribution of His48 to the catalytic activity of BT3686 is discussed.
27
Brown-Borg, Holly. "SOMATOTROPIC SIGNALING IN HEALTH AND LONGEVITY". Innovation in Aging 6, Supplement_1 (1 novembre 2022): 91. http://dx.doi.org/10.1093/geroni/igac059.361.
Testo completoAbstract (sommario):
Abstract The endocrine system is highly integrated and regulates growth, reproduction, metabolism, and stress responses that influence aging. Reduced growth hormone (GH) signaling extends health and lifespan in part, by altering metabolism maintaining enhanced insulin sensitivity and defense mechanisms. Diet composition affects metabolism and GH status integrates these nutrient signals, modulating metabolic responses that result in age-related disease susceptibility. Two pathways affected by somatotropic signaling include methionine and lipid metabolism. GH appears to regulate oxidative defense and the methionine pathway via enzymes that affect S-adenosyl-methionine, glutathione, DNA methylation, and detoxification activities. We also have evidence that GH deficient mice escape fatty liver disease when fed high-fat diets. Together our work and others indicate that GH plays a significant role in an organism’s ability to respond to nutrients and cellular stressors by regulating factors that counter stress, modulating metabolic responsiveness to nutrients, and detoxification of endogenous and exogenous compounds.
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Rafiei, Vahideh, Heriberto Vélëz e Georgios Tzelepis. "The Role of Glycoside Hydrolases in Phytopathogenic Fungi and Oomycetes Virulence". International Journal of Molecular Sciences 22, n. 17 (28 agosto 2021): 9359. http://dx.doi.org/10.3390/ijms22179359.
Testo completoAbstract (sommario):
Phytopathogenic fungi need to secrete different hydrolytic enzymes to break down complex polysaccharides in the plant cell wall in order to enter the host and develop the disease. Fungi produce various types of cell wall degrading enzymes (CWDEs) during infection. Most of the characterized CWDEs belong to glycoside hydrolases (GHs). These enzymes hydrolyze glycosidic bonds and have been identified in many fungal species sequenced to date. Many studies have shown that CWDEs belong to several GH families and play significant roles in the invasion and pathogenicity of fungi and oomycetes during infection on the plant host, but their mode of function in virulence is not yet fully understood. Moreover, some of the CWDEs that belong to different GH families act as pathogen-associated molecular patterns (PAMPs), which trigger plant immune responses. In this review, we summarize the most important GHs that have been described in eukaryotic phytopathogens and are involved in the establishment of a successful infection.
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Trepp, Roman, Martin Flück, Christoph Stettler, Chris Boesch, Michael Ith, Roland Kreis, Hans Hoppeler et al. "Effect of GH on human skeletal muscle lipid metabolism in GH deficiency". American Journal of Physiology-Endocrinology and Metabolism 294, n. 6 (giugno 2008): E1127—E1134. http://dx.doi.org/10.1152/ajpendo.00010.2008.
Testo completoAbstract (sommario):
Adult-onset growth hormone (GH) deficiency (GHD) is associated with insulin resistance and decreased exercise capacity. Intramyocellular lipids (IMCL) depend on training status, diet, and insulin sensitivity. Using magnetic resonance spectroscopy, we studied IMCL content following physical activity (IMCL-depleted) and high-fat diet (IMCL-repleted) in 15 patients with GHD before and after 4 mo of GH replacement therapy (GHRT) and in 11 healthy control subjects. Measurements of insulin resistance and exercise capacity were performed and skeletal muscle biopsies were carried out to assess expression of mRNA of key enzymes involved in skeletal muscle lipid metabolism by real-time PCR and ultrastructure by electron microscopy. Compared with control subjects, patients with GHD showed significantly higher difference between IMCL-depleted and IMCL-repleted. GHRT resulted in an increase in skeletal muscle mRNA expression of IGF-I, hormone-sensitive lipase, and a tendency for an increase in fatty acid binding protein-3. Electron microscopy examination did not reveal significant differences after GHRT. In conclusion, variation of IMCL may be increased in patients with GHD compared with healthy control subjects. Qualitative changes within the skeletal muscle (i.e., an increase in free fatty acids availability from systemic and/or local sources) may contribute to the increase in insulin resistance and possibly to the improvement of exercise capacity after GHRT. The upregulation of IGF-I mRNA suggests a paracrine/autocrine role of IGF-I on skeletal muscle.
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Granado, Miriam, Ana I. Martín, Mª Ángeles Villanúa e Asunción López-Calderón. "Experimental arthritis inhibits the insulin-like growth factor-I axis and induces muscle wasting through cyclooxygenase-2 activation". American Journal of Physiology-Endocrinology and Metabolism 292, n. 6 (giugno 2007): E1656—E1665. http://dx.doi.org/10.1152/ajpendo.00502.2006.
Testo completoAbstract (sommario):
Chronic arthritis induces cachexia associated with an inhibition of the growth hormone (GH)-insulin-like growth factor-I (IGF-I) system and an activation of the E3 ubiquitin-ligating enzymes muscle atrophy F-box (MAFbx) and muscle Ring finger 1 (MuRF1) in the skeletal muscle. The aim of this work was to study the role of cyclooxygenase (COX)-2 in chronic arthritis-induced cachexia. Arthritis was induced in rats by Freund's adjuvant injection, and the effects of two COX inhibitors (indomethacin, a nonspecific inhibitor, and meloxicam, a selective COX-2 inhibitor on pituitary GH and on liver and serum IGF-I levels) were tested. Arthritis decreased body weight gain and GH and liver IGF-I gene expression. In the arthritic rats, both inhibitors, indomethacin and meloxicam, prevented the inhibitory effect of arthritis on body weight gain. Indomethacin and meloxicam administration to arthritic rats increased pituitary GH and liver IGF-I mRNA as well as serum levels of IGF-I. These data suggest that induction of COX-2 during chronic inflammation is involved in the inhibition of the GH-IGF-I axis and in the body weight loss. In the gastrocnemius muscle, arthritis increased the gene expression of tumor necrosis factor (TNF)-α, the E3 ubiquitin-ligating enzymes MAFbx and MuRF1, as well as of IGF-I and IGF-binding protein-5 (IGFBP-5). Inhibition of COX-2 by meloxicam administration increased gastrocnemius weight and decreased MAFbx, MuRF1, TNF-α, and IGFBP-5 gene expression. In summary, our data indicate that chronic arthritis-induced cachexia and muscle wasting are mediated by the COX-2 pathway resulting in a decreased GH-IGF-I secretion and increased expression of MAFbx and MuRF1 mRNA.
31
Igarashi, Kiyohiko, Takuya Ishida, Chiaki Hori e Masahiro Samejima. "Characterization of an Endoglucanase Belonging to a New Subfamily of Glycoside Hydrolase Family 45 of the Basidiomycete Phanerochaete chrysosporium". Applied and Environmental Microbiology 74, n. 18 (1 agosto 2008): 5628–34. http://dx.doi.org/10.1128/aem.00812-08.
Testo completoAbstract (sommario):
ABSTRACT The wood decay fungus Phanerochaete chrysosporium has served as a model system for the study of lignocellulose conversions, but aspects of its cellulolytic system remain uncertain. Here, we report identifying the gene that encodes the glycoside hydrolase (GH) family 45 endoglucanase (EG) from the fungus, cloning the cDNA, determining its heterologous expression in the methylotrophic yeast Pichia pastoris, and characterizing the recombinant protein. The cDNA consisted of 718 bp, including an open reading frame encoding a 19-amino-acid signal peptide, a 7-amino-acid presequence at the N-terminal region, and a 180-amino-acid mature protein, which has no cellulose binding domain. Analysis of the amino acid sequence revealed that the protein has a low similarity (<22%) to known fungal EGs belonging to the GH family 45 (EGVs). No conserved domain of this family was found by a BLAST search, suggesting that the protein should be classified into a new subdivision of this GH family. The recombinant protein has hydrolytic activity toward amorphous cellulose, carboxylmethyl cellulose, lichenan, barley β-glucan, and glucomannan but not xylan. Moreover, a synergistic effect was observed with the recombinant GH family 6 cellobiohydrolase from the same fungus toward amorphous cellulose as a substrate, indicating that the enzyme may act in concert with other cellulolytic enzymes to hydrolyze cellulosic biomass in nature.
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Sjögren, Klara, Kin-Chuen Leung, Warren Kaplan, Margaret Gardiner-Garden, James Gibney e Ken K. Y. Ho. "Growth hormone regulation of metabolic gene expression in muscle: a microarray study in hypopituitary men". American Journal of Physiology-Endocrinology and Metabolism 293, n. 1 (luglio 2007): E364—E371. http://dx.doi.org/10.1152/ajpendo.00054.2007.
Testo completoAbstract (sommario):
Muscle is a target of growth hormone (GH) action and a major contributor to whole body metabolism. Little is known about how GH regulates metabolic processes in muscle or the extent to which muscle contributes to changes in whole body substrate metabolism during GH treatment. To identify GH-responsive genes that regulate substrate metabolism in muscle, we studied six hypopituitary men who underwent whole body metabolic measurement and skeletal muscle biopsies before and after 2 wk of GH treatment (0.5 mg/day). Transcript profiles of four subjects were analyzed using Affymetrix GeneChips. Serum insulin-like growth factor I (IGF-I) and procollagens I and III were measured by RIA. GH increased serum IGF-I and procollagens I and III, enhanced whole body lipid oxidation, reduced carbohydrate oxidation, and stimulated protein synthesis. It induced gene expression of IGF-I and collagens in muscle. GH reduced expression of several enzymes regulating lipid oxidation and energy production. It reduced calpain 3, increased ribosomal protein L38 expression, and displayed mixed effects on genes encoding myofibrillar proteins. It increased expression of circadian gene CLOCK, and reduced that of PERIOD. In summary, GH exerted concordant effects on muscle expression and blood levels of IGF-I and collagens. It induced changes in genes regulating protein metabolism in parallel with a whole body anabolic effect. The discordance between muscle gene expression profiles and metabolic responses suggests that muscle is unlikely to contribute to GH-induced stimulation of whole body energy and lipid metabolism. GH may regulate circadian function in skeletal muscle by modulating circadian gene expression with possible metabolic consequences.
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Kuo, Tzer-Min, Hui-Ting Hsu, Cheng-Yen Wei, Ming-Tain Lai e Chun-Te Chen. "Abstract 6138: High Globo-H expression associated with poor survival of gastric cancer patients and enriched PD-L1 expression". Cancer Research 82, n. 12_Supplement (15 giugno 2022): 6138. http://dx.doi.org/10.1158/1538-7445.am2022-6138.
Testo completoAbstract (sommario):
Abstract Background: Globo series antigens have been implicated in playing important roles in enhancing tumor growth through protecting tumor cells from apoptosis, suppressing T cell activity in the tumor microenvironment and promoting endothelial cell angiogenesis. Globo-H (GH), a globo-series glycosphingolipid (GSL) antigen that is synthesized by key enzymes β1,3-galactosyltransferase V (β3GalT5), fucosyltransferase (FUT) 1 and 2, is highly expressed on a variety of epithelial cancers rendering it a promising target for cancer immunotherapy. GH is reported to associate the EGFR mutant and PD-L1 expression in non-small cell lung cancer (NSCLC) patients. In addition, GH-targeting antibody-drug conjugate (ADC) OBI-999 has been demonstrated an excellent tumor growth inhibition potency in animal models across multiple cancer types including gastric cancer (GC). This study aims to further investigate the GH roles in GC. Methods: Prognostic roles of β3GalT5, FUT1 and FUT2 in GC patients were accessed through the “Kaplan-Meier plotter” database. The level of GH expression was evaluated in clinical adenocarcinoma samples from 105 patients with GC by immunohistochemistry (IHC) using H-score. Microwestern protein array analysis was performed in sorted GC NCI-N87 cells. FACS methods were also employed to measure the levels of PD-L1 and phospho-EGFRs in multiple cancer cell lines. Results: Significant correlations were observed between high mRNA expression of synthesized key enzymes and worse overall survival (OS)/post-progression survival for all 498 GC patients. Positive GH expression (H score≥20; 33.3%) was significantly associated with a poor disease specific survival in all samples (at 15 years; p=0.029), a poor OS in poorly differentiated tumors (p=0.033), and invasiveness (p=0.013), indicating GH expression was a potential prognostic factor in GC. Sorted NCI-N87 cells with high level of endogenous GH expression showed a relatively greater proliferative activity compared with cells expressing low level of GH. Microwestern array analysis on sorted cells indicated upregulations of phospho-AKT/P38/JNK, Cyclin D1 and Cyclin E1 protein in high GH expression NCI-N87 cells, which implicated a mechanistic link between high GH and tumor promoting signals in GC. In addition, GH level was shown to be correlated with cell surface expression level of PD-L1 in NCI-N87, SNU-16, HCC-1428, ACHN, and TKI-resistant H1975 NSCLC cancer cells. Higher phospho-EGFRs (Tyr1068 and Tyr1173) were detected in high GH level of H1975 cells, which is consistent with the results from previous studies showing association between GH level and EGFR mutant/PD-L1 expression in NSCLC. Conclusions: GH level was associated with the survival of GC patients and positively correlated with cell surface PD-L1 expression in vitro. Therefore, GH-targeting therapy has a potential application for the treatment of GC patients. Citation Format: Tzer-Min Kuo, Hui-Ting Hsu, Cheng-Yen Wei, Ming-Tain Lai, Chun-Te Chen. High Globo-H expression associated with poor survival of gastric cancer patients and enriched PD-L1 expression [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 6138.
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Cao, Hang, Maria Mikkelsen, Mateusz Lezyk, Ly Bui, Van Tran, Artem Silchenko, Mikhail Kusaykin et al. "Novel Enzyme Actions for Sulphated Galactofucan Depolymerisation and a New Engineering Strategy for Molecular Stabilisation of Fucoidan Degrading Enzymes". Marine Drugs 16, n. 11 (1 novembre 2018): 422. http://dx.doi.org/10.3390/md16110422.
Testo completoAbstract (sommario):
Fucoidans from brown macroalgae have beneficial biomedical properties but their use as pharma products requires homogenous oligomeric products. In this study, the action of five recombinant microbial fucoidan degrading enzymes were evaluated on fucoidans from brown macroalgae: Sargassum mcclurei, Fucus evanescens, Fucus vesiculosus, Turbinaria ornata, Saccharina cichorioides, and Undaria pinnatifida. The enzymes included three endo-fucoidanases (EC 3.2.1.-GH 107), FcnA2, Fda1, and Fda2, and two unclassified endo-fucoglucuronomannan lyases, FdlA and FdlB. The oligosaccharide product profiles were assessed by carbohydrate-polyacrylamide gel electrophoresis and size exclusion chromatography. The recombinant enzymes FcnA2, Fda1, and Fda2 were unstable but were stabilised by truncation of the C-terminal end (removing up to 40% of the enzyme sequence). All five enzymes catalysed degradation of fucoidans containing α(1→4)-linked l-fucosyls. Fda2 also degraded S. cichorioides and U. pinnatifida fucoidans that have α(1→3)-linked l-fucosyls in their backbone. In the stabilised form, Fda1 also cleaved α(1→3) bonds. For the first time, we also show that several enzymes catalyse degradation of S. mcclurei galactofucan-fucoidan, known to contain α(1→4) and α(1→3) linked l-fucosyls and galactosyl-β(1→3) bonds in the backbone. These data enhance our understanding of fucoidan degrading enzymes and their substrate preferences and may assist development of enzyme-assisted production of defined fuco-oligosaccharides from fucoidan substrates.
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Azariadis, Kalliopi, Nikolaos K. Gatselis, George K. Koukoulis e Georgios N. Dalekos. "Glycogenic hepatopathy as a cause of severe deranged liver enzymes in a young patient with type 1 diabetes mellitus". BMJ Case Reports 12, n. 3 (marzo 2019): e228524. http://dx.doi.org/10.1136/bcr-2018-228524.
Testo completoAbstract (sommario):
Glycogenic hepatopathy (GH) is a rare complication of poorly controlled type 1 diabetes mellitus (T1DM). We present a 19-year-old woman with T1DM and autoimmune thyroiditis who admitted to our department because of abrupt onset intermittent abdominal pain in the right upper quadrant accompanied by laboratory evidence of acute anicteric hepatitis. Physical examination revealed significant hepatomegaly but the common imagining studies were negative. Following exclusion of common causes of acute hepatitis and because of the presence of smooth muscle antibodies in a young female patient with already established two autoimmune diseases, a liver biopsy was performed in order to exclude the potential presence of autoimmune hepatitis. However, liver histology showed typical findings of GH. Intense treatment targeting strict glycemic control resulted in normalisation of liver biochemistry. This case underlines that GH should be considered as a rare cause of acute hepatitis in T1DM patients with poor glycemic control.
36
Molina, Manon, Thomas Prévitali, Claire Moulis, Gianluca Cioci e Magali Remaud-Siméon. "The role of the C domain in the thermostability of GH70 enzymes investigated by domain swapping". Amylase 6, n. 1 (1 gennaio 2022): 11–19. http://dx.doi.org/10.1515/amylase-2022-0002.
Testo completoAbstract (sommario):
Abstract Sucrose-active enzymes belonging to the glycoside hydrolase (GH) family 70 are attractive tools for the synthesis of oligosaccharides, polysaccharides or glycoconjugates. However, their thermostability is an important issue for the development of robust and cost-effective enzyme-based processes. Indeed, GH70 enzymes are mesophilic and no thermophilic representatives have been described so far. Furthermore, structurally guided engineering is a challenge given the size of these proteins (120 to 250 kDa) and their organization in five domains. Herein, we have investigated the possible role of the domain C in the stability of GH70 enzymes. The alternansucrase (ASR) is the most stable enzyme of the GH70 family. Structural comparison of ASR to other GH70 enzymes highlighted the compactness of its domain C. We assumed that this atypical structure might be involved in the stability of this enzyme and decided to introduce this domain in another much less stable GH70 enzyme of known three-dimensional structure, the branching sucrase GBD-CD2. The chimeric GBD-CD2 exhibited a lower specific activity on sucrose substrate but its specificity was unchanged with the enzyme remaining specific for the branching of dextran via α-1,2 linkage formation. Interestingly, the chimera showed a higher melting temperature and residual activity than the wild-type enzyme after 10 min incubation at 30 °C showing that the domain C can affect GH70 enzyme stability and could be a potential target of both random or rational mutagenesis to further improve their stability.
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Parmar, Nishant, Muslim Atiq, Lee Austin, Ross A. Miller, Thomas Smyrk e Kabir Ahmed. "Glycogenic Hepatopathy: Thinking Outside the Box". Case Reports in Gastroenterology 9, n. 2 (9 luglio 2015): 221–26. http://dx.doi.org/10.1159/000437048.
Testo completoAbstract (sommario):
Glycogenic hepatopathy (GH) remains underrecognized in adults as most clinicians mistake it for the more common hepatic abnormality associated with uncontrolled diabetes mellitus in this age group, non-alcoholic fatty liver disease. This is also complicated by the fact that both entities are indistinguishable on liver ultrasound. We herein describe a similar predicament in which a young adult female presented with bilateral upper quadrant abdominal pain, tender hepatomegaly, lactic acidosis and a >10-fold increase in liver enzymes, which worsened after the administration of high-dose steroids. Despite intravenous normal saline resuscitation, serum transaminitis persisted in a fluctuating manner. Ultimately, a liver biopsy confirmed GH. Biochemically, GH is driven by high amounts of both circulating glucose and insulin or by the administration of high-dose steroids. Improving glycemic control is the mainstay of treatment for GH. However, in our case, improvement in glycated hemoglobin of just 0.6% was enough to achieve symptomatic relief, supporting recent claims of the involvement of other identified factors in disease development.
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Ali Abulmeaty, Mahmoud Mustafa, Ali Madi Almajwal, Mohamed Farouk ElSadek, Mohamed Y. Berika e Suhail Razak. "Metabolic Effects of Testosterone Hormone Therapy in Normal and Orchiectomized Male Rats: From Indirect Calorimetry to Lipolytic Enzymes". International Journal of Endocrinology 2019 (28 novembre 2019): 1–10. http://dx.doi.org/10.1155/2019/7546385.
Testo completoAbstract (sommario):
Background and Aim. Changes in total energy expenditure (TEE) and substrate metabolism may help explain the metabolic actions of testosterone (T). This study measured respiratory quotient (RQ), TEE, ghrelin, insulin, and key lipolysis enzyme concentrations in relation to body weight (wt) and food intake (FI) in both normal and bilaterally orchiectomized rats with/without T treatment. Methods. In total, thirty-two male Wistar rats (300–400 g) were divided into four groups (n = 8/group), including (a) sham-operated and vehicle-injected group (Sham), (b) T-treated sham group (T-Sham) for which sham-operated rats were injected with IM testosterone undecanoate (100 mg/kg, for one week), (c) orchiectomy and vehicle-injected group (Orch), and (d) T-replaced orchiectomy group (T-Orch). After one week, FI and wt were automatically recorded, indirect calorimetry parameters were measured, and blood samples were collected to measure T, ghrelin, insulin, growth hormone (GH), glucose, hormone-sensitive lipase (HSL), adipocyte triglyceride lipase (ATGL), free fatty acids (FFA), and lipid profiles. Results. Orchiectomy decreased ghrelin, GH, and insulin levels, increased TEE and RQ, and lowered FI and wt. The T-Orch group exhibited increased levels of ghrelin (3-fold), insulin, GH, blood levels of lipolysis products, TEE, and FI in addition to reduced glucose levels (P<0.05). This group demonstrated no significant changes in wt. In the T-Sham group, T increased ghrelin and insulin levels (P<0.05) with strong positive correlations (r = 0.663 and 0.644, respectively, P<0.05), increased ATGL levels, RQ toward carbohydrate utilization ranges, and TEE, and reduced HSL levels (P<0.05) with insignificant changes in FI or wt. Conclusions. T administration in orchiectomized rats significantly increased orexigenic mediators such as ghrelin and insulin without inducing any significant changes in wt. The mechanism for this finding might be the increased TEE and the stimulation of lipolysis through the ATGL enzyme. The associated rise of GH might help in interference with accumulation of lipid in adipose tissue. Apart from the effect on GH, T-Sham showed similar effects of T supplementation.
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Kintrilis, Nikolaos. "Glycogenic Hepatopathy in a Teenage Girl with Diabetes Mellitus Type 1". Series of Endocrinology, Diabetes and Metabolism 5, n. 1 (30 gennaio 2023): 1–6. http://dx.doi.org/10.54178/jsedmv5i1001.
Testo completoAbstract (sommario):
Glycogenic hepatopathy (GH) refers to a relatively rare complication of diabetes mellitus (DM) type 1 which constitutes of reversible accumulation of excess hepatic glycogen, usually manifesting in the form of liver enzyme elevation along with hepatomegaly. The occurrence of the disorder is most commonly related to inadequate control of blood sugars. Herein, we report upon a case of an 18-year-old girl presenting with severe transaminase elevations owing to poor metabolic control, as well as the progression of her enzymes and general condition during and after her hospitalization.
40
Munugoti, Samhitha, Vamsee Reddy, Gaurav Patel, Maneesh Gaddam e Triveni Abburi. "A Case of Glycogenic Hepatopathy as a Complication of Poorly Controlled Type 1 Diabetes Mellitus". Case Reports in Endocrinology 2022 (29 settembre 2022): 1–5. http://dx.doi.org/10.1155/2022/8939867.
Testo completoAbstract (sommario):
A 23-year-old African American male with a medical history significant for poorly controlled type 1 diabetes mellitus (T1DM) presented with abdominal pain and vomiting. His laboratory workup was consistent with diabetic ketoacidosis (DKA). An acute elevation of liver enzymes was noted as the DKA resolved, with the alanine transferase and aspartate transferase levels elevated to more than 50 times the normal limit within the next 24 hours. Because abnormal liver function tests are found frequently in patients with type 1 diabetes mellitus, it is important to have a broad differential diagnosis. Furthermore, a low threshold of suspicion is required to identify a relatively underdiagnosed etiology like glycogenic hepatopathy (GH). This case report describes how patterns and trends of liver function tests provide important clues to the diagnosis of GH; how imaging modalities like ultrasonography, computerized tomography (CT) scan, and magnetic resonance imaging (MRI) scan could be used to differentiate GH from nonalcoholic fatty liver disease (NAFLD); and how the diagnosis of GH can be made without the need for invasive liver biopsy. The knowledge about GH should prevent its delayed diagnosis and improve the outcomes by appropriately managing uncontrolled type 1 DM.
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Feenstra, J., M. O. van Aken, W. W. de Herder, R. A. Feelders e A. J. van der Lely. "Drug-induced hepatitis in an acromegalic patient during combined treatment with pegvisomant and octreotide long-acting repeatable attributed to the use of pegvisomant". European Journal of Endocrinology 154, n. 6 (giugno 2006): 805–6. http://dx.doi.org/10.1530/eje.1.02160.
Testo completoAbstract (sommario):
We report on a patient with acromegaly who developed severe drug-induced hepatitis during combined treatment with the long-acting somatostatin-analog octreotide and the GH receptor antagonist pegvisomant. The hepatic enzyme disturbances normalized after discontinuation of pegvisomant. After rechallenge with monotherapy pegvisomant, however, the hepatic enzyme disturbances reappeared within a few weeks, indicating that most likely pegvisomant alone and not the long-acting somatostatin analog or the combination of these two drugs was responsible for this case of drug-induced hepatitis. Clinicians should be aware of this potential severe adverse drug reaction and therefore frequent control of hepatic enzymes is mandatory during treatment with pegvisomant.
42
Michlmayr, Herbert, Walter Brandes, Reinhard Eder, Christina Schümann, Andrés M. del Hierro e Klaus D. Kulbe. "Characterization of Two Distinct Glycosyl Hydrolase Family 78 α-l-Rhamnosidases from Pediococcus acidilactici". Applied and Environmental Microbiology 77, n. 18 (22 luglio 2011): 6524–30. http://dx.doi.org/10.1128/aem.05317-11.
Testo completoAbstract (sommario):
ABSTRACTα-l-Rhamnosidases play an important role in the hydrolysis of glycosylated aroma compounds (especially terpenes) from wine. Although several authors have demonstrated the enological importance of fungal rhamnosidases, the information on bacterial enzymes in this context is still limited. In order to fill this important gap, two putative rhamnosidase genes (ramandram2) fromPediococcus acidilacticiDSM 20284 were heterologously expressed, and the respective gene products were characterized. In combination with a bacterial β-glucosidase, both enzymes released the monoterpenes linalool andcis-linalool oxide from a muscat wine extract under ideal conditions. Additionally, Ram could release significant amounts of geraniol and citronellol/nerol. Nevertheless, the potential enological value of these enzymes is limited by the strong negative effects of acidity and ethanol on the activities of Ram and Ram2. Therefore, a direct application in winemaking seems unlikely. Although both enzymes are members of the same glycosyl hydrolase family (GH 78), our results clearly suggest the distinct functionalities of Ram and Ram2, probably representing two subclasses within GH 78: Ram could efficiently hydrolyze only the synthetic substratep-nitrophenyl-α-l-rhamnopyranoside (Vmax= 243 U mg−1). In contrast, Ram2 displayed considerable specificity toward hesperidin (Vmax= 34 U mg−1) and, especially, rutinose (Vmax= 1,200 U mg−1), a disaccharide composed of glucose and rhamnose. Both enzymes were unable to hydrolyze the flavanone glycoside naringin. Interestingly, both enzymes displayed indications of positive substrate cooperativity. This study presents detailed kinetic data on two novel rhamnosidases, which could be relevant for the further study of bacterial glycosidases.
43
Du, Jonathan J., Erik H. Klontz, Marcelo E. Guerin, Beatriz Trastoy e Eric J. Sundberg. "Structural insights into the mechanisms and specificities of IgG-active endoglycosidases". Glycobiology 30, n. 4 (7 giugno 2019): 268–79. http://dx.doi.org/10.1093/glycob/cwz042.
Testo completoAbstract (sommario):
Abstract The conserved N-glycan on Asn297 of immunoglobulin G (IgG) has significant impacts on antibody effector functions, and is a frequent target for antibody engineering. Chemoenzymatic synthesis has emerged as a strategy for producing antibodies with homogenous glycosylation and improved effector functions. Central to this strategy is the use of enzymes with activity on the Asn297 glycan. EndoS and EndoS2, produced by Streptococcus pyogenes, are endoglycosidases with remarkable specificity for Asn297 glycosylation, making them ideal tools for chemoenzymatic synthesis. Although both enzymes are specific for IgG, EndoS2 recognizes a wider range of glycans than EndoS. Recent progress has been made in understanding the structural basis for their activities on antibodies. In this review, we examine the molecular mechanism of glycosidic bond cleavage by these enzymes and how specific point mutations convert them into glycosynthases. We also discuss the structural basis for differences in the glycan repertoire that IgG-active endoglycosidases recognize, which focuses on the structure of the loops within the glycoside hydrolase (GH) domain. Finally, we discuss the important contributions of carbohydrate binding modules (CBMs) to endoglycosidase activity, and how CBMs work in concert with GH domains to produce optimal activity on IgG.
44
Barrios, Vicente, Laura M. Frago, Sandra Canelles, Santiago Guerra-Cantera, Eduardo Arilla-Ferreiro, Julie A. Chowen e Jesús Argente. "Leptin Modulates the Response of Brown Adipose Tissue to Negative Energy Balance: Implication of the GH/IGF-I Axis". International Journal of Molecular Sciences 22, n. 6 (11 marzo 2021): 2827. http://dx.doi.org/10.3390/ijms22062827.
Testo completoAbstract (sommario):
The growth hormone (GH)/insulin-like growth factor I (IGF-I) axis is involved in metabolic control. Malnutrition reduces IGF-I and modifies the thermogenic capacity of brown adipose tissue (BAT). Leptin has effects on the GH/IGF-I axis and the function of BAT, but its interaction with IGF-I and the mechanisms involved in the regulation of thermogenesis remains unknown. We studied the GH/IGF-I axis and activation of IGF-I-related signaling and metabolism related to BAT thermogenesis in chronic central leptin infused (L), pair-fed (PF), and control rats. Hypothalamic somatostatin mRNA levels were increased in PF and decreased in L, while pituitary GH mRNA was reduced in PF. Serum GH and IGF-I concentrations were decreased only in PF. In BAT, the association between suppressor of cytokine signaling 3 and the IGF-I receptor was reduced, and phosphorylation of the IGF-I receptor increased in the L group. Phosphorylation of Akt and cyclic AMP response element binding protein and glucose transporter 4 mRNA levels were increased in L and mRNA levels of uncoupling protein-1 (UCP-1) and enzymes involved in lipid anabolism reduced in PF. These results suggest that modifications in UCP-1 in BAT and changes in the GH/IGF-I axis induced by negative energy balance are dependent upon leptin levels.
45
Rindler, M. J., e M. G. Traber. "A specific sorting signal is not required for the polarized secretion of newly synthesized proteins from cultured intestinal epithelial cells." Journal of Cell Biology 107, n. 2 (1 agosto 1988): 471–79. http://dx.doi.org/10.1083/jcb.107.2.471.
Testo completoAbstract (sommario):
Caco-2 cells, derived from human colon, have the morphological, functional, and biochemical properties of small intestinal epithelial cells. After infection with enveloped viruses, influenza virions assembled at the apical plasma membrane while vesicular stomatitis virus (VSV) particles appeared exclusively at the basolateral membrane, similar to the pattern observed in virus-infected Madin-Darby canine kidney (MDCK). When grown in Millicell filter chamber devices and labeled with [35S]methionine, Caco-2 monolayers released all of their radiolabeled secretory products preferentially into the basal chamber. Among the proteins identified were apolipoproteins AI and E, transferrin, and alpha-fetoprotein. No proteins were observed to be secreted preferentially from the apical cell surface. The lysosomal enzyme beta-hexosaminidase was also secreted primarily from the basolateral surface of the cells in the presence or absence of lysosomotropic drugs or tunicamycin, which inhibit the targetting of lysosomal enzymes to lysosomes. Neither of these drug treatments significantly affected the polarized secretion of other nonlysosomal proteins. In addition, growth hormone (GH), which is released in a nonpolar fashion from MDCK cells, was secreted exclusively from the basolateral membrane after transfection of Caco-2 cells with GH cDNA in a pSV2-based expression vector. Similar results were obtained in transient expression experiments and after selection of permanently transformed Caco-2 cells expressing GH. Since both beta-hexosaminidase and GH would be expected to lack sorting signals for polarized exocytosis in epithelial cells, these results indicate that in intestinal cells, proteins transported via the basolateral secretory pathway need not have specific sorting signals.
46
Gangoiti, Joana, Tjaard Pijning e Lubbert Dijkhuizen. "The Exiguobacterium sibiricum 255-15 GtfC Enzyme Represents a Novel Glycoside Hydrolase 70 Subfamily of 4,6-α-Glucanotransferase Enzymes". Applied and Environmental Microbiology 82, n. 2 (20 novembre 2015): 756–66. http://dx.doi.org/10.1128/aem.03420-15.
Testo completoAbstract (sommario):
ABSTRACTThe glycoside hydrolase 70 (GH70) family originally was established for glucansucrase enzymes found solely in lactic acid bacteria synthesizing α-glucan polysaccharides from sucrose (e.g., GtfA). In recent years, we have characterized GtfB and relatedLactobacillusenzymes as 4,6-α-glucanotransferase enzymes. These GtfB-type enzymes constitute the first GH70 subfamily of enzymes that are unable to act on sucrose as a substrate but are active with maltodextrins and starch, cleave α1→4 linkages, and synthesize linear α1→6-glucan chains. The GtfB disproportionating type of activity results in the conversion of malto-oligosaccharides into isomalto/malto-polysaccharides with a relatively high percentage of α1→6 linkages. This paper reports the identification of the members of a second GH70 subfamily (designated GtfC enzymes) and the characterization of theExiguobacteriumsibiricum255-15 GtfC enzyme, which is also inactive with sucrose and displays 4,6-α-glucanotransferase activity with malto-oligosaccharides. GtfC differs from GtfB in synthesizing isomalto/malto-oligosaccharides. Biochemically, the GtfB- and GtfC-type enzymes are related, but phylogenetically, they clearly constitute different GH70 subfamilies, displaying only 30% sequence identity. Whereas the GtfB-type enzyme largely has the same domain order as glucansucrases (with α-amylase domains A, B, and C plus domains IV and V), this GtfC-type enzyme differs in the order of these domains and completely lacks domain V. In GtfC, the sequence of conserved regions I to IV of clan GH-H is identical to that in GH13 (I-II-III-IV) but different from that in GH70 (II-III-IV-I because of a circular permutation of the (β/α)8barrel. The GtfC 4,6-α-glucanotransferase enzymes thus represent structurally and functionally very interesting evolutionary intermediates between α-amylase and glucansucrase enzymes.
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Gravholt, Claus Højbjerg, Rune Weis Naeraa, Sanne Fisker e Jens Sandahl Christiansen. "Body Composition and Physical Fitness Are Major Determinants of the Growth Hormone-Insulin-Like Growth Factor Axis Aberrations in Adult Turner’s Syndrome, with Important Modulations by Treatment with 17β-Estradiol1". Journal of Clinical Endocrinology & Metabolism 82, n. 8 (1 agosto 1997): 2570–77. http://dx.doi.org/10.1210/jcem.82.8.4127.
Testo completoAbstract (sommario):
The objectives of this study were to 1) study the GH-insulin-like growth factor (IGF) axis in adult untreated Turner’s syndrome compared to that in age-matched controls, 2) examine the effects of sex hormone substitution on this axis, 3) study the effects of route of administration of 17β-estradiol on the measured variables, and 4) examine the effects of sex steroids on hepatic function in Turner patients. Twenty-seven patients with Turner’s syndrome were evaluated before and during sex hormone replacement, and an age-matched control group (n = 24) was evaluated once. Main outcome variables were GH and other measures of the GH-IGF axis, body composition, maximal oxygen uptake, sex hormone-binding globulin, and hepatic enzymes and proteins. The integrated 24-h GH concentration (IC-GH; micrograms per L/24 h) was reduced in women with Turner’s syndrome (T) compared to controls [C; mean ± sd, 18.3 ± 12.0 (T) vs. 37.2 ± 29.7 (C); P = 0.007]. However, multiple regression revealed that fat-free mass (FFM) and maximal oxygen uptake were significant explanatory variables (joint r = 0.77; P < 0.0005), accounting for 60% of the variance in the 24-h IC-GH. This association was also present in controls. After adjustment for these two variables, any difference in GH concentration between Turner patients and controls disappeared. Serum IGF-I and IGF-II were identical in Turner patients and controls despite the difference in 24-h IC-GH. The level of GH-binding protein (GHBP; nanomoles per L) was higher in Turner women [1.87 ± 0.72 (T) vs. 1.22 ± 0.33 (C); P = 0.0005]; after adjustment for FFM, the difference in GHBP levels disappeared between Turner patients and controls. During sex hormone treatment a significant increase was seen in the 24-h IC-GH (P = 0.02), FFM (percentage of weight; P < 0.0005) and maximal oxygen uptake (milliliters of O2 per kg/min; P = 0.02). Serum IGF-I was unchanged, whereas serum IGF-II (micrograms per L) decreased significantly [Turner, basal (TB), vs. Turner, treatment (TT), 860 ± 135 vs. 823 ± 150; P = 0.04]. Alanine aminotransferase (units per L), γ-glutamyl transferase (units per L), and alkaline phosphatase (units per L) were significantly elevated during the basal study period, and all decreased during treatment [alanine aminotransferase, 55 ± 55 (TB) vs. 30± 20 (TT; P = 0.006); γ-glutamyl transferase, 92 ± 98 (TB) vs. 43 ± 65 (TT; P = 0.003); alkaline phosphatase, 211 ± 113 (TB) vs. 175± 54 (TT); P = 0.06]. The route of administration of 17β-estradiol did not affect its actions. In conclusion, we found the GH-IGF axis in Turner’s syndrome to be normal, with body composition and physical fitness exerting the same modifying effects on this axis as seen in the normal population. Sex hormone replacement in Turner’s syndrome is associated with normalizing effects on the GH-IGF axis, body composition, physical fitness, and hepatic function. The lowering of hepatic enzymes is a surprising and hitherto undiscovered action of sex steroids. Finally, the route of administration of 17β-estradiol is of minor importance in Turner’s syndrome.
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Madsen, Michael, Thomas Krusenstjerna-Hafstrøm, Louise Møller, Britt Christensen, Mikkel Holm Vendelbo, Steen B. Pedersen, Jan Frystyk et al. "Fat Content in Liver and Skeletal Muscle Changes in a Reciprocal Manner in Patients with Acromegaly during Combination Therapy with a Somatostatin Analog and a GH Receptor Antagonist: A Randomized Clinical Trial". Journal of Clinical Endocrinology & Metabolism 97, n. 4 (1 aprile 2012): 1227–35. http://dx.doi.org/10.1210/jc.2011-2681.
Testo completoAbstract (sommario):
Context: Pegvisomant is a GH antagonist, which is used for the treatment of acromegalic patients. It effectively blocks the hepatic and peripheral effects of GH, but transient elevations in circulating liver enzymes of unknown pathogenesis may occur, which seems to be more prevalent when the treatment is combined with a somatostatin analog (SA). Accumulation of intrahepatic lipid is a known cause of elevated liver enzymes, and there is evidence to suggest that GH impacts lipid content in liver and skeletal muscle. Objective: Our objective was to measure lipid content in liver and skeletal muscle in acromegalic patients before and after cotreatment with pegvisomant and SA as compared with SA monotherapy. Design: Eighteen acromegalic patients well controlled on SA monotherapy were randomized in a parallel study over 24 wk to 1) unchanged SA monotherapy, or 2) cotreatment with pegvisomant (15–30 mg twice a week) and SA (half the usual dosage). Setting: This was an investigator-initiated study in a single tertiary referral center. Main Outcome Measures: Intrahepatic lipid (IHL) and intramyocellular lipid (IMCL) was assessed by 1H magnetic resonance spectroscopy. Results: IHL increased in the cotreatment group compared with SA only (P = 0.002). The increase was positively correlated to weekly pegvisomant dose (r2 = 0.52; P = 0.01). By contrast, IMCL decreased in the cotreatment group compared with SA only (P = 0.01). These changes related neither to insulin sensitivity nor inflammatory markers. Conclusion: Cotreatment with pegvisomant and a reduced SA dose increase IHL and decrease IMCL compared with SA monotherapy. The clinical implications remain unclear, but increased IHL may be causally linked to the transient elevations in liver enzymes observed during pegvisomant treatment.
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Wang, Zhihui, Michal M. Masternak, Khalid A. Al-Regaiey e Andrzej Bartke. "Adipocytokines and the Regulation of Lipid Metabolism in Growth Hormone Transgenic and Calorie-Restricted Mice". Endocrinology 148, n. 6 (1 giugno 2007): 2845–53. http://dx.doi.org/10.1210/en.2006-1313.
Testo completoAbstract (sommario):
Chronic elevation of GH induces resistance to insulin and hyperinsulinemia in both humans and animals, whereas calorie restriction (CR) improves peripheral insulin sensitivity in many species. To investigate the mechanisms that lead to insulin resistance in animals with high levels of GH as well as the mechanisms that might improve insulin sensitivity, we fed GH-overexpressing transgenic mice ad libitum or subjected them to 30% CR. We then assayed the plasma adipocytokines levels related to insulin sensitivity, plasma lipid levels, and tissue triglycerides accumulation and examined adipocyte morphology. Furthermore, we evaluated mRNA expression and protein levels of enzymes or regulators involved in regulating hepatic lipid metabolism. Our results suggest that decreased plasma adiponectin, increased plasma resistin and cholesterol, and elevated levels of TNF-α and IL-6 in adipocytes may all contribute to the insulin resistance observed in GH-Tg mice. Increased accumulation of triglycerides and impaired adipocytes differentiation in GH-transgenic mice provide plausible mechanisms for the alterations of adipocytokines. Hepatic and muscle insulin resistance in these mice is probably related to excessive accumulation of fatty acids and their metabolites. An increase in plasma adiponectin and decrease in plasma IL-6, triglycerides, and cholesterol levels in response to CR may improve insulin sensitivity.
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Lange, Kai Henrik Wiborg, Fredrik Isaksson, Anders Juul, Michael Højby Rasmussen, Jens Bülow e Michael Kjær. "Growth hormone enhances effects of endurance training on oxidative muscle metabolism in elderly women". American Journal of Physiology-Endocrinology and Metabolism 279, n. 5 (1 novembre 2000): E989—E996. http://dx.doi.org/10.1152/ajpendo.2000.279.5.e989.
Testo completoAbstract (sommario):
The present study investigated whether recombinant human (rh) growth hormone (GH) combined with endurance training would have a larger effect on oxidative capacity, metabolism, and body fat than endurance training alone. Sixteen healthy, elderly women, aged 75 yr, performed closely monitored endurance training on a cycle ergometer over 12 wk. rhGH was given in a randomized, double-blinded, placebo-controlled design in addition to the training program. GH administration resulted in a doubling of serum insulin-like growth factor I levels. With endurance training, peak oxygen uptake increased by ∼18% in both groups, whereas the marked increase in muscle citrate synthase activity was 50% larger in the GH group compared with the placebo group. In addition, only the GH group revealed an increase in musclel-3-hydroxyacyl-CoA dehydrogenase activity. Body weight remained unchanged in both groups, but the GH group showed significant changes in body composition with a decrease in fat mass and an increase in lean body mass. Twenty-four-hour indirect calorimetry performed in four subjects showed a marked increase in energy expenditure with increased relative and absolute fat combustion in the two subjects receiving rhGH. In conclusion, rhGH adds to the effects of endurance training on muscle oxidative enzymes and causes a reduction in body fat in elderly women.