Teses / dissertações: "Cataboliti"

1

Tongyoo, Narongchai. "Physical and functional analysis of genes from the cam catabolic plasmid encoding probable steps in the catabolism of camphor". Thesis, University College London (University of London), 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.397983.

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2

Chou, Han Ting. "L-Lysine Decarboxylase and Cadaverine Gamma-Glutamylation Pathways in Pseudomonas Aeruginosa PAO1". Digital Archive @ GSU, 2011. http://digitalarchive.gsu.edu/biology_diss/103.

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In comparison to other Pseudomonas, P. aeruginosa grows poorly in L-lysine as a sole source of nutrient while fast growth mutants can be obtained. The proposed catabolic pathway involves lysine decarboxylation to cadaverine and its subsequent degradation through g-glutamylation pathway to d-aminovalerate and glutarate. The lysine decarboxylase A (ldcA) gene, previously identified as a member of the ArgR regulon of L-arginine metabolism, was found essential for L-lysine catabolism. The ldcA gene encodes a decarboxylase which takes L-lysine but not L-arginine as substrate. Contrarily, the ldcA expression was inducible by L-arginine but not by L-lysine. This peculiar arginine control on lysine utilization was also noted from uptake experiments. The lack of lysine-responsive control on lysine catabolism and its tight connection to arginine regulatory network provided an explanation of lysine as poor nutrient for P. aeruginosa. Catabolism of cadaverine, a product from lysine decarboxylation, was investigated and compared to that of putrescine, another diamine of similar biochemical properties that is derived from arginine and ornithine. While the g-glutamylation pathway was first reported in E. coli for putrescine utilization, an expanded version of this pathway was found in P. aeruginosa with redundant enzymes for polyamine degradation. The PauR protein was identified as a transcriptional repressor of genes for the catabolism of putrescine and cadaverine, as well as their corresponding downstream metabolites, g-aminobutyrate (GABA) and d-aminovalerate (AMV). PauR shows distinct dimer configuration after glutaraldehyde crosslinkage, and possible conformational changes could be triggered by the presence of putrescine and cadaverine, but not GABA. A newly identified ABC transport system, encoded by the agtABCD operon, was found important for the uptake of GABA and AMV; and expression of which is controlled by the AgtSR two-component system. The CbrAB two-component system was proposed to regulate the catabolite repression control protein Crc through a small RNA CrcZ. A consensus CbrB recognition sequence was proposed based on the conserved palindromic nucleotide sequence in the upstream activating sequence of the crcZ promoter. Genetic studies indicated utilization of arginine, lysine and diamines (but not histidine, GABA and AMV) might be under CbrAB regulation through the CbrAB/CrcZ/Crc system in P. aeruginosa.

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3

Madhushani, W. K. Anjana. "Multiple regulatory inputs for hierarchical control of phenol catabolism by Pseudomonas putida". Doctoral thesis, Umeå universitet, Institutionen för molekylärbiologi (Teknisk-naturvetenskaplig fakultet), 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-106878.

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Metabolically versatile bacteria have evolved diverse strategies to adapt to different environmental niches and respond to fluctuating physico-chemical parameters. In order to survive in soil and water habitats, they employ specific and global regulatory circuits to integrate external and internal signals to counteract stress and optimise their energy status. One strategic endurance mechanism is the ability to choose the most energetically favourable carbon source amongst a number on offer. Pseudomonas putida strains possess large genomes that underlie much of their ability to use diverse carbon sources as growth substrates. Their metabolic potential is frequently expanded by possession of catabolic plasmids to include the ability to grow at the expense of seemingly obnoxious carbon sources such as phenols. However, this ability comes with a metabolic price tag. Carbon source repression is one of the main regulatory networks employed to subvert use of these expensive pathways in favour of alternative sources that provide a higher metabolic gain. This thesis identifies some of the key regulatory elements and factors used by P. putida to supress expression of plasmid-encoded enzymes for degradation of phenols until they are beneficial. I first present evidence for a newly identified DNA and RNA motif within the regulatory region of the gene encoding the master regulator of phenol catabolism – DmpR. The former of these motifs functions to decrease the number of transcripts originating from the dmpR promoter, while the latter mediates a regulatory checkpoint for translational repression by Crc – the carbon repression control protein of P. putida. The ability of Crc to form repressive riboprotein complexes with RNA is shown to be dependent on the RNA chaperone protein Hfq – a co-partnership demonstrated to be required for many previously identified Crc-targets implicated in hierarchical assimilation of different carbon sources in P. putida. Finally, I present evidence for a model in which Crc and Hfq co-target multiple RNA motifs to bring about a two-tiered regulation to subvert catabolism of phenols in the face of preferred substrates – one at the level of the regulator DmpR and another at the level of translation of the catabolic enzymes.

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4

Dantas, Hugo Miguel Campelo. "Engineering hexuronic acid catabolism". Master's thesis, Universidade de Aveiro, 2013. http://hdl.handle.net/10773/11776.

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Metabolic engineering is an emerging field targeted to the improvement of pathways for the production of high-value compounds. Citrus peel is produced at an estimated 15,000,000 t per year worldwide and its disposal causes environmental problems. The main constituent of citrus peel is D-galacturonic acid. The aim of this project is to convert D-galacturonic acid to useful chemicals using genetically engineered moulds. Aspergillus niger was chosen since it is naturally a good consumer of D-galacturonic acid and produces the enzymes required for citrus peel hydrolysis. In the present study, engineered Aspergillus niger strains were used where (i) the gaaB coding for L-galactonate dehydrogenase was deleted (ΔgaaB) and (ii) the gaaB was deleted and the gaaA coding for D-galacturonate reductase was overexpressed (ΔgaaB-gaaA). These strains were used for solid-state and submerged state fermentation to convert orange peel to L-galactonate in a consolidate process. The strains were able to convert up to 87 % of Dgalacturonic acid to L-galactonate by solid-state fermentation. Another pathway that was studied was the eukaryotic D-Glucuronic acid pathway. In this pathway is a ddecarboxylase that converts 3-keto-L-gulonate to L-xylulose. The reaction is poorly characterized and the gene not known. It was tried to assay this activity in a coupled enzyme assay. In this assay Lgulonic acid is the initial substrate, an NAD-dependent L-gulonate-3-dehydrogenase (GDH) that produces the substrate for the decarboxylase. Lxylulose reductase is then detected by an NADPH-dependent L-xylulose reductase from Aspergillus niger (lxrA). To follow the reaction NADPH was monitored at 340 nm. To avoid the interference of NADH that also absorbs at 340 nm Thio-NAD+ was used for the dehydrogenase. Active GDH and lxrA were prepared and the assay tested with ammonium sulfate precipitates from bovine liver extract. A 3-keto-L-gulonate decarboxylase activity could not be detected.
A engenharia metabólica é uma área emergente que visa o aperfeiçoamento de vias metabólicas para produção de compostos valiosos. A produção mundial de casca de frutos cítricos é estimada em 15,000,000 de toneladas por ano, e o seu descarte causa problemas ambientais. O principal constituinte da casca de frutos cítricos é o ácido D-galacturónico. O objetivo deste projeto é converter o ácido D-galacturónico noutros químicos proveitosos, utilizando para tal bolores geneticamente modificados. Aspergillus niger foi escolhido por ser naturalmente um bom consumidor do ácido Dgalacturónico e produtor das enzimas necessárias à hidrólise de casca de frutos cítricos. No presente trabalho, estirpes de Aspergillus niger foram geneticamente modificados onde (i) o gene gaaB que codifica para a L-galactonato desidratase foi deletado (ΔgaaB) e (ii) o gene gaaB foi deletado e o gene gaaA que codifica para a D-galacturonato reductase se encontrava sobreexpresso (ΔgaaB-gaaA). Estas estirpes foram utilizadas para fermentação submersa e em estado sólido para converter casca de laranja em L-galactonato num processo consolidado. As estirpes foram capazes de converter, até 87 %, de ácido D-galacturónico em L-galactonato por fermentação em estado sólido. Outra via metabólica estudada foi a via eucariota do ácido glucurónico. Nesta via metabólica é uma descarboxilase que converte o 3-ceto-L-gulonato em Lxilulose. A reação ainda não está claramente caracterizada e o gene não é conhecido. Um teste enzimático acoplado foi realizado de forma a testar a sua atividade. Neste ensaio o ácido L-gulónico é o substrato inicial, uma Lgulonato- 3-desidrogenase NAD-dependente (GDH) que produz o substrato para a descarboxilase. A L-xilulose reductase é então detetada por uma Lxilulose reductase NADPH-dependente de Aspergillus niger (lxrA). Para seguir a reação, o NADPH foi monitorizado a 340 nm. Para evitar a interferência do NADH que também absorve a 340 nm, Tio-NAD+ foi usado para a desidrogenase. GDH e lxrA ativas foram preparadas e o ensaio testado com precipitados sulfato de amónio de extrato de fígado bovino. A atividade da 3-ceto-Lgulonato descarboxilase não foi detetada.

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5

Stankiewicz, Margaret J. "Oxidative catabolism of tetrahydropterins". Thesis, Aston University, 1989. http://publications.aston.ac.uk/12531/.

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Mixed labelled folic acid was administerd to rats. Exposure to N2O was used to give an insight into the major route of scission within the monoglutamate pool, results suggest that THF formed during transport from the gut lumen to the plasma is the major route of scission within the gut. Peroxides in corn oil and arising as a result of lipid peroxidation and autoxidation increase catabolism of the monoglutamate pool and decrease incorporation of administered folates into the polyglutamate pool. It is suggested that peroxides may oxidise B12 resulting in inhibition of methionine synthetase, this results in diminished polyglutamation and increased urinary excretion of 5 CH3THF. Fats undergo peroxidation within tissues, the resulting peroxides increase catabolism of the polyglutamate pool. It is suggested that the NBT assay may reflect polyglutamate breakdown. Antioxidants such as vitamin E (and DES) decrease catabolism of the monoglutamate pool. Administration of DES resulted in changes similar to those observed during malignancy, it is suggested that these changes may precede the onset of tumour development. Vitamin E elevates brain DHPR activity. Since lowered DHPR levels and disturbed THB metabolism have been observed in aging and Down's syndrome it is proposed that vitamin E therapy may prove beneficial in situations where oxidative stress is increased. Brain DHPR activity was increased on administration of peroxides suggesting that in situations of oxidative stress (which may result in increased catabolism of THB) the salvage pathway may be stimulated and loss of THB minimised. N2O exposure had no effect on THB metabolism suggesting that the stimulatory role of 5 CH3THF is due to its role as a methyl donor.

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6

Crabbe, T. B. "Studies on the adenylate cyclase and HMGCoA reductase of the yeast Saccharomyces cerevisiae". Thesis, University of Liverpool, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.233812.

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7

Birch, D. J. "Carbon catabolite repression in the yeast Saccharomyces cerevisiae". Thesis, University of Liverpool, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.372682.

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8

Jones, Melissa Kaye. "Inositol catabolism in Drosophila melanogaster". Thesis, California State University, Long Beach, 2014. http://pqdtopen.proquest.com/#viewpdf?dispub=1527384.

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myo-Inositoloxygenase (MIOX) catalyzes the first step in myo-inositol catabolism. MIOX has not been annotated in Drosophila melanogaster, but the protein encoded by the CG6910 gene is similar to the mouse MIOX protein. CG6910 "knocked-down" expression was explored using RNAi. "Knock-down" flies did not survive on inositol defined media, indicating that CG6910 encodes MIOX. Survival of these flies on sucrose defined media suggest that MIOX is not essential for development. Biochemical assays demonstrated that D. melanogaster has MIOX activity. Computational analyses revealed potential miRNA sites, and that a number of essential components are conserved. MIOX genes found in other drosopholids are highly similar to D. melanogaster MIOX, and analyses of the syntenic regions concur with established evolution. Western blot analyses showed differential expression amongst D. melanogaster from different geographic locations and between species. These studies may contribute to understanding the role of inositol catabolism in fruit fly development and diabetes.

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9

Brummett, Adam Eugene. "Enzymology of microbial dimethylsulfoniopropionate catabolism". Diss., University of Iowa, 2017. https://ir.uiowa.edu/etd/5430.

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The biosynthesis of DMSP by phytoplankton and algae has wide ranging impact on marine organisms. Release of DMSP and uptake by marine bacteria leads to the eventual catabolism of this osmolyte. Enzymatic breakdown of DMSP leads to acrylate and volatile DMS production, which is fluxed into the atmosphere. When DMS enters the atmosphere it undergoes oxidation, acting as nucleation sites for water. The nucleation of water, and the subsequent cloud formation increases the albedo and reflects solar radiation. Global climate has therefore been hypothesized to be dependent upon DMSP breakdown to DMS. The enzymatic production of acrylate is also of interest for industrial applications. Only six enzymes are known to act as a DMSP-lyase, causing the production of DMS. These enzymes are still being discovered, and until recently there was very limited analysis of the biochemical requirements for catalysis. The work presented here investigates these requirements and the structural properties that permit the elimination reaction yielding DMS.

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10

Kandasamy, Dineshkumar. "Study on yeast enzymes Urc1p and Urc4p in a novel uracil catabolism pathway (URC)". Thesis, Uppsala universitet, Institutionen för biologisk grundutbildning, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-185013.

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Purine and pyrimidine bases are the central precursors of DNA and RNA and theirintracellular concentration is balanced by three pathways- de novo, salvage and catabolicpathways. Uracil catabolism pathway has been found in several bacteria and in some fungi(including yeast). Seven genes, URC1-7 have been found to be involved in this novelpathway. There are two “unknown genes” in the yeast Lachancea (Saccharomyces) kluyveri,namelyURC1 and URC4, which play a central role in this pathway and their exact functionremains a mystery.In this project, two S. kluyveri genes, URC1&URC4, were over-expressed in the bacterialsystem and successfully purified. Our preliminary functional assay showed that uridinemonophosphate (UMP) is a likely substrate for Urc1p at pH7, 25ºC. It was shown clearly thatboth uracil and uridine were not the substrate for Urc1p. We tried to phosphorylatechemically synthesized ribosylurea using Drosophila melanogaster deoxyribonucleosidekinase and compared the activity between phosphorylated and non- phosphorylated RU atdifferent conditions. Phosphorylated ribosylurea seemed to be a likely substrate for Urc4p atpH7, 37ºC. Keywords: Uridine monophosphate (UMP), ribosylurea (RU), uracil catabolism.

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11

Grimsley, Philip George Medical Sciences Faculty of Medicine UNSW. "Receptor mediated catabolism of plasminogen activators". Awarded By:University of New South Wales. Medical Sciences, 2009. http://handle.unsw.edu.au/1959.4/44489.

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Humans have two plasminogen activators (PAs), tissue-type plasminogen activator (tPA) and urokinase-type plasminogen activator (uPA), which generate plasmin to breakdown fibrin and other barriers to cell migration. Both PAs are used as pharmaceuticals but their efficacies are limited by their rapid clearance from the circulation, predominantly by parenchymal cells of the liver. At the commencement of the work presented here, the hepatic receptors responsible for mediating the catabolism of the PAs were little understood. tPA degradation by hepatic cell lines was known to depend on the formation of binary complexes with the major PA inhibitor, plasminogen activator inhibitor type-1 (PAI-1). Initial studies presented here established that uPA was catabolised in a fashion similar to tPA by the hepatoma cell line, HepG2. Other laboratories around this time found that the major receptor mediating the binding and endocytosis of the PAs is Low Density Lipoprotein Receptor-related Protein (LRP1). LRP1 is a giant 600 kDa protein that binds a range of structurally and functionally diverse ligands including, activated α2 macroglobulin, apolipoproteins, β amyloid precursor protein, and a number of serpin-enzymes complexes, including PA??PAI-1 complexes. Further studies for the work presented here centred on this receptor. By using radiolabelled binding assays, ligand blots, and Western blots on cultured cells, the major findings are that: (1) basal LRP1 expression on HepG2 is low compared to a clone termed, HepG2a16, but appears to increase in long term culture; (2) a soluble form of LRP1, which retains ligand-binding capacity, is present in human circulation; (3) soluble LRP1 is also present in cerebral spinal fluid where its role in neurological disorders such as Alzheimer??s disease is a developing area of interest; and (4) the release of LRP1 is a mechanism conserved in evolution, possibly as distantly as molluscs. The discovery, identification, and characterisation of soluble LRP1 introduces this protein in the human circulation, and presents a possible further level of regulation for its associated receptor system.

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12

Rhys-Williams, William. "The microbial catabolism of 4-nitrotoluene". Thesis, Bangor University, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.359756.

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13

Robertson, Colin Daniel. "Anerobic catabolism of glycerol by Klebsiellae". Thesis, University of Oxford, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.330032.

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14

Platt, Alison. "A study of 4-hydroxy-2-oxovalerate aldolase from the meta pathway operon of the nah plasmid pWW60-22". Thesis, Bangor University, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.239887.

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15

Winson, Michael Kenneth. "Molecular biological studies on catabolic plasmids". Thesis, Bangor University, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.305927.

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16

Beck, Susan A. "Catabolic factors in tumour-induced cachexia". Thesis, Aston University, 1989. http://publications.aston.ac.uk/12508/.

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A transplantable colon adenocarcinoma of the mouse (MAC16) was utilized as a model of human cancer cachexia. The MAC16 tumour produced extensive weight loss in the host at small tumour burdens and without a reduction in either food or fluid intake. The weight loss was characterised by a decrease in both carcass fat and muscle mass which were directly proportional to the weight of the tumour. The weight loss has been correlated with the production of circulatory catabolic factors by the tumour, which degrade host muscle and adipose tissue in vitro. These factors were further characterised and have been shown to be distinct and separable by gel exclusion chromatography. The proteolytic factors (molecular weight > 150k daltons) were distinguishable from the lipolytic factors which appeared related with molecular weights of approximately 3.0, 1.5 and 0.7k daltons. Lipolytic factors of the same molecular weights were identified in other tumour models and in the body fluids of tumour-bearing animals and cancer patients. These factors were not present in healthy individuals or in patients with other weight-losing conditions. Various temperatures studied reversed the weight loss seen in the cachexia induced by the MAC16 adenocarcinoma in vivo. The effects of these treatments could be linked in vitro to the inhibition of the catabolic factors produced by the tumour. These results suggest that these factors may be responsible for the cachexia the tumour confers on its host. These factors may be useful in the understanding and therapy of cancer cachexia.

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17

Rafudeen, M. S. "Investigation of carbon catabolite repression in Clostridium beijerinckii NCIMB 8052". Doctoral thesis, University of Cape Town, 2001. http://hdl.handle.net/11427/4326.

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Summary in English.
Includes bibliographical references.
The substrate basis for the industrial acetone-butanol-ethanol (ABE) fermentations, has been agricultural products rich in starch or sucrose, and employed taxonomically distinct amylolytic and saccharolytic solventogenic clostridial strains respectively. There is evidence to suggest that the utilization of these substrates is subject to carbon catabolite repression. In Gram-positive bacteria, carbon catabolite repression is controlled by a global regulatory mechanism, central to which is an imperfect palindromic sequence, the cre element, which is recognized by a protein of the GalR-LacI family, the CcpA protein. A ccpA homologue, regA, has been previously identified in C. acetobutylicum NCP262 and successfully complemented a B. subtilis ccpA mutant strain. The sucrose operon from C. beijerinckii NCIMB 8052, scrARBK, has been characterised at the physiological and genetic levels with the ScrR repressor found to negatively auto-regulate the operon.

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18

Mayer, Stephen Armond. "Carbon catabolite repression of yeast CBP1 mRNA 3' end formation". Diss., The University of Arizona, 1990. http://hdl.handle.net/10150/185336.

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CBP1 is a yeast nuclear gene encoding a mitochondrial protein that stabilizes the 5' end of cytochrome b (cob) pre-mRNA. Cytochrome b is the only mitochondrially synthesized component of the respiratory chain Complex III. Since the nuclearly-encoded subunits of this complex are regulated at the transcriptional level by catabolite repression, we hypothesized that CBP1 might be similarly regulated. To test the idea that transcriptional regulation of CBP1 could coordinate an increase in cytochrome b mRNA stability with an increase in nuclearly-encoded Complex III subunit production, we characterized the change in abundance of CBP1 mRNA during derepression on a non-fermentable carbon source. Poly A⁺ RNA from derepressed yeast was examined by Northern analyses with cRNA probes from CBP1. Both 2.2 kb and 1.3 kb transcripts were detected. The 1.3 kb mRNA lacks approximately 900 base-pairs of the 3'-end of the 2.2 kb mRNA, which encodes the carboxyl-terminal 250 amino acid residues of the CBP1 coding sequence. Northern analyses of RNA isolated from deletion/insertion mutants of CBP1 and from strains which overexpress CBP1 mRNA demonstrated that both mRNAs are transcribed from the CBP1 gene. Furthermore, we have demonstrated that the levels of the two CBP1 mRNAs are reciprocally regulated by the carbon source in the growth medium. Having proposed that regulation of 3' end formation dictates the amount of each CBP1 transcript we now show that a 146 bp fragment from the middle of CBP1 is sufficient to direct carbon source-regulated production of two transcripts when inserted into the yeast URA3 gene. This fragment contains seven polyadenylation sites for the wild-type 1.2 kb mRNA, as mapped by sequence analysis of CBPl cDNA clones. Deletion mutations upstream of the polyadenylation sites abolished formation of the 1.2 kb transcript, whereas deletion of three of the sites only led to a reduction in abundance of the 1.2 kb mRNA. Though none of the experiments showed whether the 1.2 kb mRNA is formed solely by 3' processing, or if processing at this site is coupled to premature transcription termination, our results do indicate that regulation of the abundance of both CBP1 transcripts is contro11ed by elements in a short segment of the gene that directs 3' end formation of the 1.2 kb transcript, a unique case in yeast.

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19

Floderus, Eugenie. "Aminopeptidases and arginine catabolism in oral straptococci". Stockholm : Kongl. Carolinska Medico Chirurgiska Institutet, 1990. http://books.google.com/books?id=bMZpAAAAMAAJ.

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20

Broome, Malcolm Charles, e mikewood@deakin edu au. "Aspects of milk protein catabolism by lactobacilli". Deakin University. School of Sciences, 1988. http://tux.lib.deakin.edu.au./adt-VDU/public/adt-VDU20050902.120502.

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Lactobacillus plantarum and subspecies of Lactobacillus casei were isolated from good quality mature Cheddar cheese and characterized with respect to metabolic functions that would allow their use in cheesemaking. In this way microbiological control of the maturation process with particular emphasis on protein catabolism was achieved. The lactobacilli isolated were selected for low growth rates (and acid production) in milk, and low proteinase activity to allow for their addition in high numbers to cheesemilk together with the normal starter flora (group N streptococci). The growth and acid production of the starter bacteria were unaffected by the presence of the lactobacilli during cheese manufacture and it was found that the added lactobacilli were able to grow and function under the conditions prevalent in Cheddar cheese during maturation. It was also demonstrated that the lactobacilli could be grown in an artificial medium to high numbers under controlled conditions and could be harvested for the preparation of cell concentrates, a necessary characteristic for commercialization. The lactobacilli also metabolized citrate, a potential problem in cheese maturation associated with C02 production but this did not adversely affect the maturation process under the conditions used. Compared to the group N streptococci the non-starter lactobacilli possessed a proteinase system that had a higher temperature optimum and was less affected by heat and sodium chloride. They also possessed a more active peptidase system although both the lactobacilli and the starter organisms possessed a similar range of peptidases. Non-starter lactobacilli were added to normal cheese and cheese made with proteinase negative starter. The added organisms did not adversely affect manufacturing parameters and did not metabolize citrate or lead to the formation of biogenic amines. However protein catabolism rates, particularly with respect to peptide degradation, were increased, as was flavour development and intensity. It was observed that the body and texture of the cheeses was unaffected by the treatment. By controlling both the starter and non-starter microflora in the cheeses a practical system for favourably influencing cheese maturation was possible. The investigation has demonstrated that carefully selected and characterized non-starter lactobacilli can be incorporated into Cheddar cheese manufacture in order to influence flavour development during maturation. Moreover the organisms can be added to the vat stage of manufacture without causing problems to the manufacturing process. This approach is a simple cost effective means of improving the cost of Cheddar cheese production and provides an unique opportunity to improve and control quality of all Cheddar cheese produced.

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21

Walters, Nicola Jane. "Arginine and proline catabolism in Schizosaccharomyces pombe". Thesis, University of Cambridge, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.257192.

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22

Sherburn, Richard. "The microbial catabolism of metalworking fluid additives". Thesis, University of Hull, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.301630.

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23

Love, Charmaine. "PrP catabolites as determinants of TSE susceptibility". Thesis, University of Edinburgh, 2011. http://hdl.handle.net/1842/5709.

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Transmissible spongiform encephalopathies (TSEs) are a group of fatal neurodegenerative diseases that are characterised by long incubation periods, protein aggregation and vacuolation. During TSE pathogenesis the normal, cellular prion protein, (PrPC), which is encoded by the gene PRNP, misfolds and accumulates as abnormal disease associated prion protein, (PrPSc) within the central nervous system. Variants of the Prion protein gene are associated with susceptibility to TSE disease. For example sheep scrapie disease is modulated by several PRNP alleles, with certain alleles carried by susceptible animals being different from those carried by resistant animals. The mechanisms linking PRNP genetics and disease is poorly understood but may involve protein sequence, PrPC expression levels, and possibly differences in protein processing. Post-translational modification of PrPC leads to specific cleavage (alpha cleavage) between amino acids 115/116 of ovine PrP, producing two fragments C1 and N1. Cleavage of PrP may occur as a protective mechanism, as a response to changes in the cellular environment or as a feature of an as yet unknown biological function. In the context of TSEs, alpha cleavage may inadvertently provide a protective role by reducing available PrPC protein for conversion into PrPSc, assuming that the C1 fragment would be an inefficient substrate for conversion, the opposite theory was also proposed. The former hypothesis became the focus of this present study, with the idea that total full-length PrPC, total C1 or the ratio between full-length PrPC and C1 may be linked to differences in scrapie susceptibility. To investigate these aims the C1 fragment was measured as a percentage of total PrPC in different PRNP genotypes with varying degrees of susceptibility to scrapie and in different brain regions. This study found that PrPC alpha cleavage increased during development from the new born lamb to the adult sheep, which may have consequences for the susceptibility differences related to age. There are also variations in the amount of alpha cleavage between brain regions such as cortex and medulla that may influence scrapie strain targeting. Overall the amount of the C1 fragment in the different brain areas varied as much as 10x (range 5% to 60%). There was a significant difference in the ratio of C1 to the other PrPC forms between two PRNP genotype groups carrying the VRQ and ARQ allele but there was no correlation between C1 level and scrapie susceptibility or scrapie incubation period in our scrapie models. Alpha cleavage of PrPC also occurs in various transgenic mouse models expressing different ruminant PrP sequences. In PrPC over-expressing transgenic mouse models a higher ratio of C1 was observed, this may suggest a link between PrPC expression levels and alpha cleavage. Transgenic mice are therefore important models to further investigate the link between PrPC biology and scrapie disease phenotype. In conclusion, this thesis has shown for the first time that certain ovine PRNP alleles can influence alpha cleavage of the PrPC protein; however it appears not to be a significant indicator of TSE disease susceptibility in sheep.

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24

Wilkins, M. P. "The role of oxyhaems in haem catabolism". Thesis, Bucks New University, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.373588.

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25

Sudjadi. "Analysis of cloned genes for GABA catabolism". Thesis, University of Leicester, 1991. http://hdl.handle.net/2381/35163.

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A putative hpa+ clone has been isolated allowing an Hpa-Hpc+ mutant CD03 to growth on 4-HPA. Detection of a 4-HPA monooxygenase from extracts was unsuccessful. When it became apparent that gab genes had been cloned the emphasis switched to detailed analysis of those genes. The gab genes were isolated using suppression of a mutant CT101 defective in the sad gene. It seems that the cloned gabDT genes encoding NADP-dependent SSA dehydrogenase and GABA transaminase are responsible for these, not the gabD gene only. Possible explanation of these phenomena are described. E.coli C and K-12 cannot utilise GABA as the sole carbon source. However, E.coli K-12 can mutate to grow on GABA at 30°C but did not at 37°C without further mutation. Both types of mutants were found to have high activities of GABA utilizing enzymes. Studying clones isolated from the wild-type and mutated clones revealed there was a negative regulatory gene, gabR. E.coli K-12 can utilise GABA as the sole nitrogen source at 30°C but not at 37°C. The 1.7 kbp EcoRI-SalI fragment from the wild-type and mutated clones allowed cells to utilise GABA as the sole nitrogen source at 37°C. Thus, the fragment might encode a positive regulatory gene called "gabC". The gene order was determined to be gab"C"DTPR and there were located within the 10.1 kbp EcoRI region. Transcription of gabDTP is from the gabD to gabP direction, whereas gabR appears to be transcribed in the opposite direction. A representation of the organisation and expression of gab genes in E.coli is proposed.

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26

Lawson, Kathryn René. "Catabolism as a mechanism of polyamine detoxification". Diss., The University of Arizona, 1998. http://hdl.handle.net/10150/288919.

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Maintenance of optimal polyamine pool levels is critical for cell survival. Intracellular polyamine depletion is usually cytostatic, whereas unregulated polyamine accumulation can result in cytotoxicity. The purpose of this work was to examine the importance of polyamine depletion in cell survival, either through increased polyamine catabolism or decreased polyamine synthesis. The polyamine analogue CHENSpm, which induces apoptosis in several cell lines, was used to examine the role of polyamine catabolism in cell survival. The susceptibility of Chinese hamster ovary cells and HCT 116 human colon cells to CHENSpm-mediated toxicity was inversely correlated with the level of polyamine oxidase (PAO) activity present in each cell type. Chinese hamster ovary cells (CHO), which contained high levels of PAO, were not growth inhibited by CBENSpm, however concomitant PAO inhibition led to a moderate growth suppression. The inhibition of the diamine exporter (DAX) in addition to PAO led to a CHENSpm-mediated cytotoxic response that was manifested as apoptosis induction. HPLC analysis of CHENSpm- treated CHO cell extracts revealed the presence of an unidentified amine that was not present when PAO was inhibited. This suggests that PAO is able to utilize CHENSpm as a substrate, and that this metabolism protects cells from CHENSpm-mediated cytotoxicity. The effect of polyamine depletion in apoptosis induced by the non-steroidal anti-inflammatory drug (NSAID) sulindac was examined in cells harboring an activated Ki-ras. Cells overexpressing Ki-ras underwent an accelerated apoptosis induction with either metabolite of sulindac, however overall toxicity was unaffected in long-term survival assays. DFMO did not affect apoptosis induction by sulindac sulfone, nor did it increase sulindac sulfone toxicity in long-term survival studies. DFMO alone was selectively cytotoxic to Ki-ras transfected clones in a dose-dependent manner. Ki-ras transfection increased c-myc expression, but had no effect on ODC steady-state mRNA levels. The downregulation of N1-spermidine/spermine acetyltransferase (SSAT) seen in Ki-ras transfected cells suggests polyamine, catabolism may protect cells from DFMO-induced cytotoxicity. These studies demonstrate that polyamine, catabolism may play an important role in cell survival under conditions of suboptimal polyamine levels.

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27

Kuhn, Hallie. "Regulation of Yolk Catabolism in Early Embryogenesis". Thesis, Harvard University, 2015. http://nrs.harvard.edu/urn-3:HUL.InstRepos:23845424.

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Yolk provides an important source of nutrients during the early development of oviparous (non-platental) organisms. In addition to phosphate and lipids, it is com- posed mainly of vitellogenin proteins packed into membrane-bound compartments called yolk platelets. Catabolism of yolk is initiated by acidification of the yolk platelet, leading to the activation of cathepsin-like proteases that degrade yolk contents, but it is unknown how this process is triggered. Using maternal shRNA technology in Drosophila melanogaster embryos we find that yolk catabolism depends on components of the Tor pathway, a well-characterized regulator of cellular metabolism. Knockdown of Tor also leads to severe nuclear fragmentation, abnormal gastrulation, and an increased ratio of AMP/ATP. This phenotype is more severe than inhibition of Tor in later development, or in cell culture models, suggesting that Tor may have additional functions during early development. Additionally, we identify a downstream target of Tor, Atg1, as necessary for yolk catabolism. Atg1 is responsible for initiation of autophagy, a process that de- grades both protein and organelles within the cell. While Atg1 is required for a burst of spatially-regulated autophagy during late cellularization, autophagy is not required for yolk catabolism. We find that knockdown of Atg1, but not downstream autophagy proteins, can rescue shRNA-Tor embryos, suggesting that Atg1’s role in yolk cataboilism may be through regulation of Tor. Last, we find that Rheb, a GTPase responsible for activation of Tor on the lysosome membrane, is present on Xenopus laevis yolk platelets. Therefore, regulation of yolk catabolism by the Tor pathway may function in a similar manner to Tor’s activity on the lysosome. Together, this work connects the conserved Tor and Atg1 metabolic sensing pathways to yolk catabolism, and may provide insight into the metabolic regulation of lysosomes more generally.
Systems Biology

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28

Hildebrandt, Tatjana [Verfasser]. "Amino acid catabolism in plants / Tatjana Hildebrandt". Hannover : Gottfried Wilhelm Leibniz Universität Hannover, 2019. http://d-nb.info/1204458634/34.

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29

Damaraju, Sridevi. "Analysis of proteins involved in chlorophyll catabolism". Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät I, 2011. http://dx.doi.org/10.18452/16322.

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Der Abbau des Chlorophyll (Chl) ist ein Prozess, der typischerweise während der Blattseneszenz und der Reifung von Früchten und Samen stattfindet. Eine Störung dieses koordinierten Prozesses unter Frostbedingungen verzögert den Chl-Abbau und ist ein grosses Hindernis bei der Herstellung von hochwertigem Rapsöl. Der Abbau von Chl zu farblosen Kataboliten erfolgt in einer Serie von enzymatischen Schritten und wird durch die Chlorophyllase begonnen (Chlase). Es wurde vorgeschlagen, dass ein wasserlösliches Chl Protein (WSCP) den Transport des Chl von der Thylakoidmembran zum Wirkort der Chlase übernimmt. Weiterhin wurde angenommen, dass die Steigerungen der Genexpressionen dieser frühen Schritte den Prozess des Chl-Abbaus beschleunigen. In der vorliegenden Arbeit werden die Auswirkungen der Überexpression der Chlase aus Citrus clementii (CcCHLASE) und von WSCP aus Blumenkohl (Cau-WSCP) in transgenen Tabakpflanzen analysiert. Dazu wurde die cDNA Sequenz der CcCHLASE in E. coli exprimiert und mittels in vitro Experimenten die Hydrolysierung von Chl durch die Chlase bestätigt. Anschließend wurden CcCHLASE exprimierende Tabakmutanten generiert und drei T1-Linien wurden unter verschiedenen Stress- und Seneszenzbedingungen untersucht. Die Chlase überexprimierenden Linien zeigten unter allen getesteten Bedingungen einen im Vergleich zum Wildtyp erhöhten Chlide a Gehalt. Trotzdem unterschied sich die Menge an Endkataboliten in diesen Mutanten nicht vom Wildtyp. Andererseits zeigten WSCP überexprimierende Linien zwar keine erhöhten Chlide a Gehalte jedoch erhöhte Protochlorophyllid-(Pchlide)-Level. Das deutet auf eine Rolle des WSCP als Speichermolekül für Chlorophyllvorstufen hin. Die photoprotektive Funktion des WSCP wurde zusätzlich in WSCP überexprimierenden Linien bestätigt. Diese zeigen im Vergleich zu Wildtyp-Tabakpflanzen auch bei hohen Lichtintensitäten von 700 – 900 µmol Photonen m-2 s-1 verringerte Gehalte an Zeaxanthin und reduzierte Peroxidaseaktivitäten.
Chlorophyll (Chl) catabolism is characteristically seen during leaf senescence, fruit ripening and seed maturation. Disruption of this coordinated process under frost conditions delays Chl breakdown and is a great concern in rapeseed oil production. The present work addresses this problem by studying the effect of enhanced Chl catabolism in genetically modified tobacco plants. Chl is catabolised to colourless catabolites through a series of enzymatic reactions initiated by Chlorophyllase (Chlase). A water soluble chlorophyll protein (WSCP) has been proposed to transport Chl from thylakoid membranes to the site of action of Chlase. It was assumed that enhancing the gene expression of these early events in Chl catabolism would increase the Chl breakdown process. The present work analysed the overexpression of Chlase from Citrus clementii (CcCHLASE) and WSCP gene from cauliflower (Cau-WSCP) in modified tobacco plants. Initially, the cDNA sequence of CcCHLASE was expressed in E. coli and in vitro tests confirmed the hydrolytic activity of Chlase on Chl. Subsequently, tobacco plants overexpressing CcCHLASE were generated and three T1 lines were analysed at various stress and senescence conditions. The in vivo production of Chlorophyllide (Chlide) indicated the extent of increased Chl breakdown. The Chlase overexpressor lines showed higher Chlide a steady state levels under all tested conditions in comparison to the WT tobacco plants. However, the end catabolites did not show much difference from WT plants. On the other hand, WSCP overexpressor lines did not show any increase in Chlide a levels, but demonstrated an increased protochlorophyllide (Pchlide) levels. This suggested the role of WSCP as a storage molecule of Chl precursors. Additionally, photoprotective function of WSCP was confirmed in WSCP overexpressors, by lower zeaxanthin levels and peroxidase activity even at high light intensities of 700 – 900 µmol photons m-2 s-1 in comparison to the WT tobacco plants.

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30

Durkin, Shannon M. "Complementation of the sor-4 Gene of Neurospora Crassa". Youngstown State University / OhioLINK, 2000. http://rave.ohiolink.edu/etdc/view?acc_num=ysu1004562481.

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31

Sonoda, Yo. "Structural and functional analysis of a sporulation protein Spo0M from Bacillus subtilis". Kyoto University, 2016. http://hdl.handle.net/2433/215587.

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Kyoto University (京都大学)
0048
新制・課程博士
博士(農学)
甲第19761号
農博第2157号
新制||農||1039(附属図書館)
学位論文||H28||N4977(農学部図書室)
32797
京都大学大学院農学研究科応用生命科学専攻
(主査)教授三上文三, 教授加納健司, 教授喜多恵子
学位規則第4条第1項該当

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32

La, Cecilia Daniele. "Comprehensive modeling of agrochemicals biodegradation in soil: A multidisciplinary approach to make informed choices to protect human health and the environment". Thesis, The University of Sydney, 2019. http://hdl.handle.net/2123/20691.

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Numerical models are used to predict the dynamics of potentially hazardous pesticides in soil. Those models may account for fundamental processes affecting pesticide dynamics, such as environmental and edaphic conditions, water flow, degradation, and sorption. However, those models lack the ability to account for complex biogeochemical and ecological feedbacks, and thus create challenges in achieving robust predictions. In particular, no attention has been paid on the coupled mechanistic description of microbial dynamics and soil organic matter cycling and the implications on agrochemicals biodegradation and soil and groundwater quality. This thesis aims to provide this description by developing a comprehensive framework through a multidisciplinary approach. Microbiological regulation of pesticide dynamics was investigated by coupling theoretical and numerical approaches with experiments carried out in our environmental laboratory or sourced from the literature. We propose the use of reaction networks to highlight the possibly multiple pesticide degradation pathways and the feedbacks with macronutrient cycles. Biochemically-similar pathways are mediated by a specific microbial functional group, which represents the microbial community carrying out particular functions; these functions are biodegradation of pesticides and metabolism of carbon-, nitrogen-, and phosphorus-containing molecules. We describe biochemical reactions by means of Michaelis-Menten-Monod (MMM) kinetics. Indeed, MMM parameters fully encompass the microbial life strategies including rapid growth, high affinity for substrates, or high substrate consumption efficiency. Michaelis-Menten terms allow us to include microbial competition for substrates, growth inhibition, and the memory-associated catabolite repression herein presented. Finally, the relevance of the described processes was quantified by means of sensitivity analyses. The latter are crucial to explore the range of likely outcomes under a suite of scenarios, thus allowing one to make informed choices. Agrochemicals are accumulating in soil and water resources worldwide. The proposed high-level process coupling approach is urged to develop sustainable plans in accordance with Nature-based strategies to cope with environmental changes.

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33

Horton, William Henry Clay. "Characterization of the Components of Carbon Catabolite Repression in Clostridium perfringens". Thesis, Virginia Tech, 2004. http://hdl.handle.net/10919/36119.

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Clostridium perfringens is a versatile pathogen capable of causing a wide array of diseases, ranging from clostridial food poisoning to tissue infections such as gas gangrene. An important factor in virulence as well as in the distribution of C. perfringens is its ability to form an endospore. The symptoms of C. perfringens food poisoning are directly correlated to the release of an enterotoxin at the end of the sporulation process. The sporulation process in C. perfringens is subject to carbon catabolite repression (CCR) by sugars, especially glucose. CCR is a regulatory pathway that alters transcription based on carbon source availability. In Gram-positive bacteria, the HPr kinase/phosphatase is responsible for this nutritional sensing by phosphorylating or dephosphorylating the serine-46 residue of HPr. HPr-Ser-P then forms a complex with the transcriptional regulator CcpA to regulate transcription. We were able to show here that purified recombinant C. perfringens HPr kinase/phosphatase was able to phosphorylate the serine-46 residue of HPr. When the codon for this serine residue is mutated through PCR mutagenesis to encode alanine, phosphorylation could not take place. We have also shown that in gel retardation assays, CcpA and HPr-Ser-P were able to bind to two DNA fragments containing putative C. perfringens CRE-sites, sequences where CcpA binds to regulate transcription. The genome sequence of a food poisoning strain of C. perfringens was searched for potential CRE-sites using degenerate sequences designed to match those CRE-sites CcpA was shown to bind. DNA fragments containing these newly identified CRE-sites were then used in gel retardation assays to determine whether CcpA binds to these CRE-sites, making them candidates for CCR regulation. These results, combined with comparisons of metabolic characteristics of a ccpA- strain versus wild-type C. perfringens, provide evidence that CcpA participates in the regulation of carbon catabolite repression in the pathogenic bacterium C. perfringens
Master of Science

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34

Sabiston, C. Paul. "The role of catabolin in experimental osteoarthritis". Thesis, University of British Columbia, 1985. http://hdl.handle.net/2429/24909.

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The pathogenesis of osteoarthritis (OA) is complex, but likely involves destruction of articular cartilage by endogenous enzymes (Dingle 1979). Factors controlling this are not well understood. Cetabolin, a 21,000 molecular weight peptide structurally end functionally related to interleukin-1, stimulates living but not killed chondrocytes in vitro to degrade their matrix (Fell and Jubb 1977, Saklatvala et al. 1983), suggesting it is not itself a degradative enzyme but functions as a control factor. The work in this thesis investigated the possible role of cetabolin in the pethogenesis of OA by measuring catabolin production by cultures of synovium excised from the canine anterior cruciate ligament transection model of OA. Normal cenine synovium in culture was shown to produce a factor which can stimulate the release of glycoseminoglycens from living cenine articular cartilage in culture. The total emount of cetebolin produced by cultures of synovium from experimentally induced OA synovium is statistically significantly greater (p<0.05) than that produced by normal synovium. When calculated per gram of synovium, there was no statistically significant difference. This suggests that a possible role for cetebolin in the pathogenesis of OA might be related to the degree of synovial hypertrophy.
Medicine, Faculty of
Graduate

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35

Lemley, Caleb Owens. "Alterations in progesterone catabolic enzymes by insulin". Morgantown, W. Va. : [West Virginia University Libraries], 2007. https://eidr.wvu.edu/etd/documentdata.eTD?documentid=5286.

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36

Yang, Yifan. "Catabolic responses to resistance exercise in humans". Virtual Press, 2005. http://liblink.bsu.edu/uhtbin/catkey/1317922.

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37

Peel, Michelle C. (Michelle Carolyn) Carleton University Dissertation Biology. "Catabolic genotype distributions in the Niagara watershed". Ottawa, 1996.

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38

Steward, W. P. "The structure of proteoglycans associated with normal and malignant cells". Thesis, University of Manchester, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.234215.

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39

Hou, Chunsheng 1968. "Sulfur amino acid catabolism in a piglet model". Thesis, McGill University, 2002. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=78381.

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A model was developed in growing piglets to study the use of urinary total sulfur excretion as an indicator of sulfur amino acid (SAA) catabolism and the nitrogen (N)/sulfur (S) balance ratio as an indicator of non-protein SAA storage. The recovery of administrated methionine as urinary total S over 48 hours was 106% in well-nourished piglets, but only 69% in protein malnourished piglets. The N/S balance ratio of protein malnourished piglets was lower than that of well-nourished piglets, and this ratio further decreased after methionine administration. We conclude that in a protein malnourished state, relatively more S than N is retained and a significant portion of the S derived from administrated methionine is retained in non-protein pools. These results demonstrate that urinary total S excretion can provide an accurate measure of SAA catabolism; and the N/S balance ratio can provide valuable information about non-protein SAA storage in growing piglets.

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40

Carvallo, Sergio Luis Fuenmayor. "Catabolism of naphthalene by Pseudomonas sp. strain U2". Thesis, Bangor University, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.263318.

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41

Yang, M. "Catabolism and bioactivity of bradykinin and related peptides". Thesis, Queen's University Belfast, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.557857.

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Bradykinin and related peptides (BRPs) are common components of amphibian defensive skin secretions, particularly in ranid and phyllomedusine frogs and in bombinid toads. BRPs are known to be highly vasoactive with some possessing potent effects on blood vessel formation (angiogenesis) - a process known to be initiated by direct effects on endothelial cells. Human microvessel endothelial (HMEC) cells are a stable laboratory cell line often used for preliminary screening in such studies of BRP function. Since these cells are the starting points for fundamental biological studies, we examined their catabolism of bradykinin (BK) and maximakinin (MK). MK represents an N-terminally extended version of the former but with higher potency. Both BK and MK were broken down by proteases present on HMEC cells with half-lives of 5h and 2h, respectively. However, as two major metabolites of MK retained the receptor-active site of BK, the true half-life of non- active metabolite generation was 5h (BK) and 9h (MK). Bradykinin antagonists, kinestatin and QUB919, both from amphibian skin, were not degraded by HMEC cells and their presence did not interfere with the degradation of BK or MK. Using primer sets designed for bradykinin Bland B2 receptors, transcripts of appropriate size were amplified from an HMEC cell cDNA library. Bradykinin-related peptides are thus catabolised in different ways by HMEC cells and the cells were shown to contain polyadenylated mRNAs for both bradykinin receptor sub-types, Bland B2. To examine other functions of BRPs, we screened reverse phase HPLC fractions of venoms and defensive skin secretions to identify, structurally characterise and ultimately chemically-synthesise novel peptides to examine their effects on bradykinin activity using smooth muscle bioassays. Many BRPs exhibited anti- cancer and anti-microbial functions in our experiments giving us a broader perspective for further research in the BRP field. · ';.

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42

James, V. J. "Regulation of xenobiotic catabolism in plant tissue culture". Thesis, Cardiff University, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.380205.

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43

Le, Tissier Paul Roussel. "The biochemical genetics of purine catabolism in mice". Thesis, University of Reading, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.236393.

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44

Wade, David Patrick. "Receptor-mediated catabolism of lipoproteins by the liver". Thesis, Imperial College London, 1989. http://hdl.handle.net/10044/1/47700.

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45

Raucoules, Daniel. "Catabolites plasmatiques des monoamines et depressions : etude preliminaire". Aix-Marseille 2, 1989. http://www.theses.fr/1989AIX20954.

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46

Ummadi, Madhavi. "Tryptophan Catabolism in Brevibacterium linens BL2". DigitalCommons@USU, 2002. https://digitalcommons.usu.edu/etd/5501.

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Recent studies suggest aromatic amino acid catabolism by starter lactococci and flavor adjunct bacteria have a significant impact on off-flavor development during Cheddar cheese ripening. We hypothesized that a flavor adjunct bacterium, Brevibacterium linens BL2, produces off-flavor compounds from aromatic amino acid metabolism that will have a detrimental impact on cheese flavor. The mechanism of tryptophan (Trp) catabolism in Brevibacterium linens BL2, was investigated in a chemically defined medium during incubation in laboratory conditions (no carbohydrate, pH 6.50, 220 rpm, 25°C) and cheese-like conditions (no carbohydrate, 4% NaCl, static incubation, l5°C). In laboratory conditions, metabolic studies and enzyme assays confirmed that Trp was converted to kynurenine and anthranilic acid. However, cells incubated in cheese-like conditions did not utilize Trp, indicating that these enzymes are not likely to be involved in formation of Trp compounds associated with off-flavors in Cheddar cheese. In an attempt to verify the metabolic activity of the cells during incubation by monitoring the amino acid metabolism in chemically defined medium inoculated with B. linens BL2, a capillary electrophoresis-laser-induced fluorescence method was developed that could separate, detect, and quantitate 18 amino acids within 38 min. The data indicated that B. linens BL2 was metabolically active. Presumably, the cells will be metabolically active and metabolize amino acids in cheese as well. The ability to determine the Trp metabolic activity of B. linens BL2 in cheese, and to quantify Trp catabolic compounds in cheese during ripening, requires a quantitative extraction procedure. An analytical method was developed to extract and quantify aromatic amino acids and Trp catabolites from cheese using capillary electrophoresis. Methanol was used to extract Cheddar cheese made with Lactococcus lactis S3 alone and in combination with B. linens BL2 to quantitatively determine the influence of BL2 on the occurrence of aromatic catabolites. All cheeses contained aromatic amino acids, indole acetic acid, and indole. The concentration and time taken for development of these compounds were significantly decreased or delayed by the addition of B. linens BL2. After 6 months of aging, the concentrations of Trp catabolites were significantly lower in cheese made with B. linens BL2. Addition of BL2 did not directly contribute to off-flavors derived from Trp catabolism in Cheddar cheese. Therefore, the hypothesis was rejected.

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47

Debailleul, Fabien. "A new expression system in Saccharomyces cerevisiae based on nitrogen catabolite regulation". Doctoral thesis, Universite Libre de Bruxelles, 2013. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/209428.

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SUMMARY

Gap1, the general amino acid permease of Saccharomyces cerevisiae, is a plasma membrane protein which is synthesized and most active under conditions of poor nitrogen supply. Under these conditions, the role of Gap1 is to scavenge external amino acids to be used as nitrogen sources or directly as building blocks for protein synthesis. Gap1 is a member of the Yeast Amino Acid Transporter (YAT) family, a family of amino acid transporters highly conserved in bacteria and fungi.

The intracellular trafficking of Gap1 has been the subject of intense investigation as well as the role of lipids (in particular sphingolipids) in its activity and folding. These studies have all been carried out in the cellular context using versatile yeast genetics as exploratory tools. While such in vivo investigations allow to identify physiologically relevant features, they do not provide the details to understand the molecular basis of these phenomena. In order to decipher the molecular features responsible for biological functions, physiological analysis must be combined with biochemical, biophysical and structural studies which typically will be performed on isolated and purified proteins.

Our work during this study fits in this trans-disciplinary approach that aims at understanding different properties of the protein: (I) how sphingolipids modulate the activity of Gap1, (II) what part of the protein, and more specifically, what residues, are implicated in its regulation and (III) what are the molecular determinants of the multi-specificity of Gap1.

At the beginning of this work, Gap1 had not been previously produced and purified. During this thesis we have identified suitable expression and purification strategies for Gap1 and initiated first characterization studies. In the process, we have developed a new expression system in S. cerevisiae based on the nitrogen catabolite repression.

The capacity of this system to express other proteins was successfully tested for two other yeast transporters (Mep2 and Uga4) and for two human proteins: MD-2, a soluble protein and Vglut1, a vesicular transporter.

Therefore, we propose our expression design as a viable alternative to existing systems of production in yeast and as a valuable tool to be tested when starting the expression of a new target.
Doctorat en Sciences
info:eu-repo/semantics/nonPublished

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48

DeGrazia, Henry. "A biophysical investigation of the mechanisms of the catabolite gene activator protein". Diss., Georgia Institute of Technology, 1988. http://hdl.handle.net/1853/25641.

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49

O'Donnell, Kevin John. "Studies on the behaviour of catabolic plasmid pWW15". Thesis, Bangor University, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.280644.

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50

White, Tommi Anna. "Structural and functional studies of proline catabolic enzymes". Diss., Columbia, Mo. : University of Missouri-Columbia, 2007. http://hdl.handle.net/10355/4760.

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Thesis (Ph.D.)--University of Missouri-Columbia, 2007.
The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on March 24, 2009) Vita. Includes bibliographical references.

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