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Articles de revues sur le sujet "S-Acylation"
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Chamberlain, Luke H., et Michael J. Shipston. « The Physiology of Protein S-acylation ». Physiological Reviews 95, no 2 (avril 2015) : 341–76. http://dx.doi.org/10.1152/physrev.00032.2014.
Texte intégralRésumé :
Protein S-acylation, the only fully reversible posttranslational lipid modification of proteins, is emerging as a ubiquitous mechanism to control the properties and function of a diverse array of proteins and consequently physiological processes. S-acylation results from the enzymatic addition of long-chain lipids, most typically palmitate, onto intracellular cysteine residues of soluble and transmembrane proteins via a labile thioester linkage. Addition of lipid results in increases in protein hydrophobicity that can impact on protein structure, assembly, maturation, trafficking, and function. The recent explosion in global S-acylation (palmitoyl) proteomic profiling as a result of improved biochemical tools to assay S-acylation, in conjunction with the recent identification of enzymes that control protein S-acylation and de-acylation, has opened a new vista into the physiological function of S-acylation. This review introduces key features of S-acylation and tools to interrogate this process, and highlights the eclectic array of proteins regulated including membrane receptors, ion channels and transporters, enzymes and kinases, signaling adapters and chaperones, cell adhesion, and structural proteins. We highlight recent findings correlating disruption of S-acylation to pathophysiology and disease and discuss some of the major challenges and opportunities in this rapidly expanding field.
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Shipston, Michael J. « Ion channel regulation by protein S-acylation ». Journal of General Physiology 143, no 6 (12 mai 2014) : 659–78. http://dx.doi.org/10.1085/jgp.201411176.
Texte intégralRésumé :
Protein S-acylation, the reversible covalent fatty-acid modification of cysteine residues, has emerged as a dynamic posttranslational modification (PTM) that controls the diversity, life cycle, and physiological function of numerous ligand- and voltage-gated ion channels. S-acylation is enzymatically mediated by a diverse family of acyltransferases (zDHHCs) and is reversed by acylthioesterases. However, for most ion channels, the dynamics and subcellular localization at which S-acylation and deacylation cycles occur are not known. S-acylation can control the two fundamental determinants of ion channel function: (1) the number of channels resident in a membrane and (2) the activity of the channel at the membrane. It controls the former by regulating channel trafficking and the latter by controlling channel kinetics and modulation by other PTMs. Ion channel function may be modulated by S-acylation of both pore-forming and regulatory subunits as well as through control of adapter, signaling, and scaffolding proteins in ion channel complexes. Importantly, cross-talk of S-acylation with other PTMs of both cysteine residues by themselves and neighboring sites of phosphorylation is an emerging concept in the control of ion channel physiology. In this review, I discuss the fundamentals of protein S-acylation and the tools available to investigate ion channel S-acylation. The mechanisms and role of S-acylation in controlling diverse stages of the ion channel life cycle and its effect on ion channel function are highlighted. Finally, I discuss future goals and challenges for the field to understand both the mechanistic basis for S-acylation control of ion channels and the functional consequence and implications for understanding the physiological function of ion channel S-acylation in health and disease.
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Hemsley, Piers A. « S-acylation in plants : an expanding field ». Biochemical Society Transactions 48, no 2 (2 avril 2020) : 529–36. http://dx.doi.org/10.1042/bst20190703.
Texte intégralRésumé :
S-acylation is a common yet poorly understood fatty acid-based post-translational modification of proteins in all eukaryotes, including plants. While exact roles for S-acylation in protein function are largely unknown the reversibility of S-acylation indicates that it is likely able to play a regulatory role. As more studies reveal the roles of S-acylation within the cell it is becoming apparent that how S-acylation affects proteins is conceptually different from other reversible modifications such as phosphorylation or ubiquitination; a new mind-set is therefore required to fully integrate these data into our knowledge of plant biology. This review aims to highlight recent advances made in the function and enzymology of S-acylation in plants, highlights current and emerging technologies for its study and suggests future avenues for investigation.
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Locatelli, Carolina, Kimon Lemonidis, Christine Salaun, Nicholas C. O. Tomkinson et Luke H. Chamberlain. « Identification of key features required for efficient S-acylation and plasma membrane targeting of sprouty-2 ». Journal of Cell Science 133, no 21 (9 octobre 2020) : jcs249664. http://dx.doi.org/10.1242/jcs.249664.
Texte intégralRésumé :
ABSTRACTSprouty-2 is an important regulator of growth factor signalling and a tumour suppressor protein. The defining feature of this protein is a cysteine-rich domain (CRD) that contains twenty-six cysteine residues and is modified by S-acylation. In this study, we show that the CRD of sprouty-2 is differentially modified by S-acyltransferase enzymes. The high specificity/low activity zDHHC17 enzyme mediated restricted S-acylation of sprouty-2, and cysteine-265 and -268 were identified as key targets of this enzyme. In contrast, the low specificity/high activity zDHHC3 and zDHHC7 enzymes mediated more expansive modification of the sprouty-2 CRD. Nevertheless, S-acylation by all enzymes enhanced sprouty-2 expression, suggesting that S-acylation stabilises this protein. In addition, we identified two charged residues (aspartate-214 and lysine-223), present on opposite faces of a predicted α-helix in the CRD, which are essential for S-acylation of sprouty-2. Interestingly, mutations that perturbed S-acylation also led to a loss of plasma membrane localisation of sprouty-2 in PC12 cells. This study provides insight into the mechanisms and outcomes of sprouty-2 S-acylation, and highlights distinct patterns of S-acylation mediated by different classes of zDHHC enzymes.
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BAÑÓ, M. Carmen, S. Caroline JACKSON et I. Anthony MAGEE. « Pseudo-enzymatic S-acylation of a myristoylated Yes protein tyrosine kinase peptide in vitro may reflect non-enzymatic S-acylation in vivo ». Biochemical Journal 330, no 2 (1 mars 1998) : 723–31. http://dx.doi.org/10.1042/bj3300723.
Texte intégralRésumé :
Covalent attachment of a variety of lipid groups to proteins is now recognized as a major group of post-translational modifications. S-acylation of proteins at cysteine residues is the only modification considered dynamic and thus has the potential for regulating protein function and/or localization. The activities that catalyse reversible S-acylation have not been well characterized and it is not clear whether both the acylation and the deacylation steps are regulated, since in principle it would be sufficient to control only one of them. Both apparently enzymatic and non-enzymatic S-acylation of proteins have previously been reported. Here we show that a synthetic myristoylated c-Yes protein tyrosine kinase undecapeptide undergoes spontaneous S-acylation in vitro when using a long chain acyl-CoA as acyl donor in the absence of any protein. The S-acylation was dependent on myristoylation of the substrate, the length of the incubation period, temperature and substrate concentration. When COS cell fractions were added to the S-acylation reaction no additional peptide:S-acyltransferase activity was detected. These results are consistent with the possibility that membrane-associated proteins may undergo S-acylation in vivo by non-enzymatic transfer of acyl groups from acyl-CoA. In this case, the S-acylation-deacylation process could be controlled by a regulated depalmitoylation mechanism.
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Zheng, Lihua, Peng Liu, Qianwen Liu, Tao Wang et Jiangli Dong. « Dynamic Protein S-Acylation in Plants ». International Journal of Molecular Sciences 20, no 3 (29 janvier 2019) : 560. http://dx.doi.org/10.3390/ijms20030560.
Texte intégralRésumé :
Lipid modification is an important post-translational modification. S-acylation is unique among lipid modifications, as it is reversible and has thus attracted much attention. We summarize some proteins that have been shown experimentally to be S-acylated in plants. Two of these S-acylated proteins have been matched to the S-acyl transferase. More importantly, the first protein thioesterase with de-S-acylation activity has been identified in plants. This review shows that S-acylation is important for a variety of different functions in plants and that there are many unexplored aspects of S-acylation in plants.
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Hines, P. J. « Location, location, S-acylation ». Science 353, no 6295 (7 juillet 2016) : 133–34. http://dx.doi.org/10.1126/science.353.6295.133-f.
Texte intégral
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Lemonidis, Kimon, Oforiwa A. Gorleku, Maria C. Sanchez-Perez, Christopher Grefen et Luke H. Chamberlain. « The Golgi S-acylation machinery comprises zDHHC enzymes with major differences in substrate affinity and S-acylation activity ». Molecular Biology of the Cell 25, no 24 (décembre 2014) : 3870–83. http://dx.doi.org/10.1091/mbc.e14-06-1169.
Texte intégralRésumé :
S-acylation, the attachment of fatty acids onto cysteine residues, regulates protein trafficking and function and is mediated by a family of zDHHC enzymes. The S-acylation of peripheral membrane proteins has been proposed to occur at the Golgi, catalyzed by an S-acylation machinery that displays little substrate specificity. To advance understanding of how S-acylation of peripheral membrane proteins is handled by Golgi zDHHC enzymes, we investigated interactions between a subset of four Golgi zDHHC enzymes and two S-acylated proteins—synaptosomal-associated protein 25 (SNAP25) and cysteine-string protein (CSP). Our results uncover major differences in substrate recognition and S-acylation by these zDHHC enzymes. The ankyrin-repeat domains of zDHHC17 and zDHHC13 mediated strong and selective interactions with SNAP25/CSP, whereas binding of zDHHC3 and zDHHC7 to these proteins was barely detectable. Despite this, zDHHC3/zDHHC7 could S-acylate SNAP25/CSP more efficiently than zDHHC17, whereas zDHHC13 lacked S-acylation activity toward these proteins. Overall the results of this study support a model in which dynamic intracellular localization of peripheral membrane proteins is achieved by highly selective recruitment by a subset of zDHHC enzymes at the Golgi, combined with highly efficient S-acylation by other Golgi zDHHC enzymes.
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Zhang, Lian, Karyn Foster, Qiuju Li et Jeffrey R. Martens. « S-acylation regulates Kv1.5 channel surface expression ». American Journal of Physiology-Cell Physiology 293, no 1 (juillet 2007) : C152—C161. http://dx.doi.org/10.1152/ajpcell.00480.2006.
Texte intégralRésumé :
The number of ion channels expressed on the cell surface shapes the complex electrical response of excitable cells. An imbalance in the ratio of inward and outward conducting channels is unfavorable and often detrimental. For example, over- or underexpression of voltage-gated K+ (Kv) channels can be cytotoxic and in some cases lead to disease. In this study, we demonstrated a novel role for S-acylation in Kv1.5 cell surface expression. In transfected fibroblasts, biochemical evidence showed that Kv1.5 is posttranslationally modified on both the NH2 and COOH termini via hydroxylamine-sensitive thioester bonds. Pharmacological inhibition of S-acylation, but not myristoylation, significantly decreased Kv1.5 expression and resulted in accumulation of channel protein in intracellular compartments and targeting for degradation. Channel protein degradation was rescued by treatment with proteasome inhibitors. Time course experiments revealed that S-acylation occurred in the biosynthetic pathway of nascent channel protein and showed that newly synthesized Kv1.5 protein, but not protein expressed on the cell surface, is sensitive to inhibitors of thioacylation. Sensitivity to inhibitors of S-acylation was governed by COOH-terminal, but not NH2-terminal, cysteines. Surprisingly, although intracellular cysteines were required for S-acylation, mutation of these residues resulted in an increase in Kv1.5 cell surface channel expression, suggesting that screening of free cysteines by fatty acylation is an important regulatory step in the quality control pathway. Together, these results show that S-acylation can regulate steady-state expression of Kv1.5.
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Schroeder, H., R. Leventis, S. Shahinian, P. A. Walton et J. R. Silvius. « Lipid-modified, cysteinyl-containing peptides of diverse structures are efficiently S-acylated at the plasma membrane of mammalian cells. » Journal of Cell Biology 134, no 3 (1 août 1996) : 647–60. http://dx.doi.org/10.1083/jcb.134.3.647.
Texte intégralRésumé :
A variety of cysteine-containing, lipid-modified peptides are found to be S-acylated by cultured mammalian cells. The acylation reaction is highly specific for cysteinyl over serinyl residues and for lipid-modified peptides over hydrophilic peptides. The S-acylation process appears by various criteria to be enzymatic and resembles the S-acylation of plasma membrane-associated proteins in various characteristics, including inhibition by tunicamycin. The substrate range of the S-acylation reaction encompasses, but is not limited to, lipopeptides incorporating the motifs myristoylGC- and -CXC(farnesyl)-OCH3, which are reversibly S-acylated in various intracellular proteins. Mass-spectrometric analysis indicates that palmitoyl residues constitute the predominant but not the only type of S-acyl group coupled to a lipopeptide carrying the myristoylGC- motif, with smaller amounts of S-stearoyl and S-oleoyl substituents also detectable. Fluorescence microscopy using NBD-labeled cysteinyl lipopeptides reveals that the products of lipopeptide S-acylation, which cannot diffuse between membranes, are in almost all cases localized preferentially to the plasma membrane. This preferential localization is found even at reduced temperatures where vesicular transport from the Golgi complex to the plasma membrane is suppressed, strongly suggesting that the plasma membrane itself is the preferred site of S-acylation of these species. Uniquely among the lipopeptides studied, species incorporating an unphysiological N-myristoylcysteinyl- motif also show substantial formation of S-acylated products in a second, intracellular compartment identified as the Golgi complex by its labeling with a fluorescent ceramide. Our results suggest that distinct S-acyltransferases exist in the Golgi complex and plasma membrane compartments and that S-acylation of motifs such as myristoylGC- occurs specifically at the plasma membrane, affording efficient targeting of cellular proteins bearing such motifs to this membrane compartment.
Thèses sur le sujet "S-Acylation"
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Freyermuth, Chloé. « Approches de chémobiologie pour quantifier la S-acylation des protéines ». Electronic Thesis or Diss., Bordeaux, 2025. http://www.theses.fr/2025BORD0029.
Texte intégralRésumé :
La S-acylation est une modification post-traductionnelle des protéines qui correspond à la formation d’une liaison covalente entre un acide gras et un résidu cystéine. L'ajout de ce groupement hydrophobe peut modifier la localisation des protéines et affecter leur structure et/ou leur stabilité. La réversibilité et le dynamisme de cette modification enzymatique lui confèrent un rôle de régulateur dans les cellules, avec une implication observée dans de nombreux processus biologiques importants. Des aberrations dans les cycles de S-acylation ont été associées à différentes maladies humaines, telles que des cancers ou des maladies neurodégénératives. Les méthodes de protéomique existantes reposent principalement sur la quantification relative de la S-acylation des protéines. Notamment, il n’existe pas de méthodes permettant de quantifier précisément les variations des niveaux de S-acylation de chaque cystéine. Ce projet de thèse s'est concentré sur le développement d'une méthode de quantification de la S-acylation des cystéines dans un seul échantillon de protéome. Nous avons choisi de baser la méthode sur le marquage séquentiel et différentiel des cystéines libres et des cystéines S-acylées à l'aide d'une paire de sondes chimiques marquées isotopiquement. Les sondes ont des structures identiques, composées d'un électrophile pour alkyler les cystéines, d'une fonction alcyne, et d’isotopes légers et lourds permettant d’introduire une différence de masse (sonde « légère » (12C, 14N) et sonde « lourde » (13C, 15N)). Les cystéines marquées sont ensuite couplées par réaction click à un agent de capture portant un motif biotine et un azoture. Après digestion par la trypsine, les peptides contenant des cystéines sont enrichis à l'aide de billes de NeutrAvidin. Suite à leur élution des billes, les peptides marqués sont analysés par LC-MS/MS. L'analyse MS fournit un ratio de marquage lourd/léger pour les cystéines marquées dans un seul échantillon de protéome, révélant le pourcentage de S-acylation de ces cystéines. Les outils chimiques (sondes et agents de capture) ont été synthétisés et le pipeline a été développé, avec la sélection des différents paramètres des étapes de traitement des protéines à l'aide d'analyses qualitatives (Western blot). Des analyses par protéomique ont ensuite permis d'étudier plus en détail des variables, telles que les couples de sondes et d’agents de capture, les paramètres d'analyse LC-MS/MS et le traitement des données pour calculer les pourcentages de S-acylation. La méthode a été appliquée pour détecter les changements des niveaux de S-acylation suite à un stimulus externe, permettant l’acquisition de nouvelles informations sur certaines voies de signalisation et des processus biologiques associés. Les optimisations de la méthode seront poursuivies, notamment avec la comparaison de sondes possédant de nouvelles structures et une automatisation du pipeline. Nous prévoyons une large application de la méthode développée à l'étude des niveaux de S-acylation des cystéines des protéines et de leur lien avec différentes pathologies, ce qui pourrait révéler des traitements innovantsS-acylation is a post-translational modification of proteins involving the covalent attachment of a fatty acid to cysteine residues. This addition of a hydrophobic moiety can alter the protein localisation, and can also affect their structure and/or stability. The reversibility and dynamism of this enzymatic modification enable it to play a regulatory role in cellular processes, with involvement in various biological functions. Aberrant S-acylation has been linked to a variety of human diseases, including cancers or neurodegenerative diseases. Existing proteomics methods are mostly based on relative quantification of the S-acylation of proteins. Tools to precisely quantify changes in S-acylation levels of each cysteine residue are noticeably lacking. This thesis project focuses on the development of a method to quantify the S-acylation levels of cysteine residues in a single proteome sample. The method relies on the sequential and differential labelling of free cysteines and S-acylated cysteines using a pair of isotopically-tagged chemical probes. The probes have identical structures, each composed of a cysteine-reactive electrophile and an alkyne handle, with a mass difference introduced by light and heavy isotopes (“light” probe (12C, 14N) and “heavy” probe (13C, 15N)). The labelled cysteines are then coupled by click reaction to an azide-capture reagent bearing a biotin moiety. Following tryptic digestion, cysteine-containing peptides are enriched using NeutrAvidin beads, and the eluted labelled peptides are analysed by LC-MS/MS. MS analysis provides heavy-to-light ratios for each labelled cysteine within a single proteome sample, which reveals the percentage of S-acylation of the cysteines. The chemical tools were synthesised and the workflow was developed with the selection of protein treatments’ parameters using qualitative analysis approaches (e.g., Western blotting). Proteomics analyses allowed further refinement of key variables, including the combination of probes and capture reagents, the LC-MS/MS analysis parameters, and the downstream data processing to calculate the S-acylation percentages. The method was successfully applied to detect changes in S-acylation levels upon an external stimulus, providing new insights into associated signalling pathways and biological processes. Optimisations of the workflow will be pursued, notably by comparing new probes and automating the pipeline. We anticipate that the developed method will have broad applications for studying the S-acylation levels of cysteine residues and their role in different pathologies, potentially revealing innovative treatments
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Leung, Wai Sang Stephane 1980. « S-acylation of fully deprotected peptides using thioesters as acyl donors ». Thesis, McGill University, 2004. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=82275.
Texte intégralRésumé :
Diverse eukaryotic proteins require the post-translational addition of S-acyl chains to cysteine residues for proper function, a process known as S-palmitoylation, or S-acylation. To study the effects of this lipid moiety, various complex methods have been developed for the preparation of synthetic lipopeptides. In order to facilitate this task, a novel technique employing readily-prepared long-chain acyl thioesters has been devised. Using S-phenylmercapto-palmitoyl thioester as well as other acyl thioesters, the fluorescent-labeled peptide, myristoyl-GCG-caBim, was S-acylated to high stoichiometry at halftimes as short as 20 min. (initial rate of S-acylation of 179.8 +/- 24.7%/hr) in homogeneous solution, without the presence of micelles or vesicles. The chemical reaction occurred regioselectively on cysteine side-chains without modification of serine or lysine derivatives of the peptide. This method was also utilized to selectively S-acylate the fully deprotected Po peptide, IRYCWLRR-NH2. Such an innovative technique should provide a useful scheme for the general synthesis of S-acylated peptides.
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Schroeder, Hans R. « S-acylation and intracellular targeting of lipid-modified proteins and model lipopeptides ». Thesis, McGill University, 2000. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=36812.
Texte intégralRésumé :
Three related studies were performed to better characterize the intracellular process of protein S-acylation in mammalian cells. The first study focused on the use of cysteinyl-containing fluorescent lipopeptides which mimic the N-terminal of various S-acylable intracellular regulatory proteins. These lipopeptides diffuse rapidly between membranes and are efficiently S-acylated by a variety of mammalian cells. S-acylation appears to be enzymatic by various criteria and is highly selective for cysteinyl as opposed to serinyl residues. Fluorescence microscopy revealed that the plasma membrane is the predominant site for intracellular S-acylation but that a second potential site localized to the Golgi apparatus may also exist.The second study examined the intracellular S-acylation of lipopeptides which mimic the carboxy-terminus of N-ras. S-acylation of lipopeptides was again specific for cysteinyl residues as opposed to serinyl residues. The exact structure of the attached prenyl group, for example the farnesyl versus geranyl group, does not affect the ability of the lipopeptide to undergo S-acylation, however, an attached moiety with sufficient hydrophobicity to promote high affinity but rapidly reversible interactions with membranes is required for efficient S-acylation. Fluorescence microscopy suggests that S-acylation of these peptides and likely N-ras protein itself occurs at the plasma membrane of mammalian cells.
The third study examined the hypothesis that proteins of different sequences may be S-acylated by distinct S-acyltransferases. Lipopeptides bearing sequences mimicking the N-termini of src-like nonreceptor protein tyrosine kinases or heterotrimeric G-protein alpha-subunits, incorporate similar ratios of [3H]palmitate/[3H]stearate following incubation of lipopeptide with cells and equal activities of [3H]palmitate and [3H]stearate. In contrast, lipopeptides which mimic the C-terminus of N-ras exhibit ratios which are significantly different from the ratios for those lipopeptides described above. These results suggest that these two groups of structurally-different lipopeptides are S-acylated by distinct S-acyltransferases within the plasma membrane. Further, lipopeptides bearing nonphysiological sequences which are preferentially S-acylated in the Golgi, incorporate radiolabeled fatty acids in ratios which are significantly different from those determined for most lipopeptides S-acylated at the plasma membrane, suggesting that distinct S-acyltransferases may exist in the plasma membrane and Golgi apparatus of mammalian cells.
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Brett, Katharina. « Molecular requirements of influenza virus hemagglutinin for site-specific S-acylation and virus replication ». Doctoral thesis, Humboldt-Universität zu Berlin, Lebenswissenschaftliche Fakultät, 2015. http://dx.doi.org/10.18452/17274.
Texte intégralRésumé :
Das Hämagglutinin (HA) des Influenzavirus ist post-translational durch S-Acylierung von drei Cysteinen modifiziert. Zwei davon befinden sich in seiner zytoplasmatischen Domäne (CD) und enthalten Palmitat und eines am Cytosol-zugewandten Ende der Transmembranregion (TMR) wird bevorzugt mit Stearat acyliert. Es wird vermutet, dass entweder die Aminosäureumgebung der Acylierungsstelle oder dessen Lage relativ zur Membran bestimmt welcher Fettsäuretyp angeheftet wird. Diese Acylierungstellen sind zudem essentiell für die Virusreplikation. Ob auch andere Aminosäuren der CD essentiell sind, ist nicht bekannt. Nach einem umfangreichen Sequenzvergleich zur Identifikation konservierter Aminosäuren wurden rekombinante Viren mit Aminosäureaustauschen in der Nähe der drei Acylierungstellen hergestellt. Diese Austausche enthielten Punktmutationen, Verschieben des TMR Cysteins in die CD sowie die Deletion der gesamten CD. Viren ohne CD und ein Austausch neben einem acylierten Cystein verhinderten die Virusreplikation. Eine konservative Substitution derselben Position, andere Austausche in TMR und CD sowie das Schieben des TMR-Cysteins in die CD dagegen beeinflussten das Viruswachstum nur schwach. Einige der mutierten Codons revertierten zur ursprünglichen oder einer neuen Aminosäure. Rekombinante Viren wurden in MDCK-Zellen und embryonierten Hühnereiern vermehrt und mittels Massenspektrometrie analysiert. Es wurden keine unteracylierten Peptide detektiert, und selbst die zwei Letalmutationen behielten die Acylierung. Punktmutationen beeinträchtigten nur mäßig den Stearat-Gehalt, wogegen die Verlagerung des TMR-Cysteins in die CD die Stearylierung praktisch eliminierte. Mehr Stearat wurde angeheftet, wenn humane Viren in Säugerzellen im Vergleich zu aviären Zellen angezüchtet wurden. Die Position einer Acylierungsstelle repräsentiert relativ zur TMR-Spanne das Hauptsignal der Stearylierung während der Sequenzkontext und der Zelltyp das Fettsäuremuster modulieren.Influenza virus’s hemagglutinin (HA) is post-translationally modified by S-acylation of three cysteines. Two are located in its cytoplasmic tail (CT) and contain palmitate and one at the end of the transmembrane region (TMR) is acylated primarily with stearate. It is hypothesized that either the acylation site’s amino acid environment or its location relative to the membrane determines which type of fatty acid is attached. Additionally, these acylation sites are essential for virus replication. Whether other amino acids in the CT are required for virus replication, is not known. Based on a comprehensive sequence comparison to identify conserved amino acids, recombinant viruses with amino acid substitutions in the vicinity of HA’s acylation sites were created. These substitutions included point mutations, shifting of a TMR cysteine to the CT and the deletion of the entire tail. The truncated tail mutation and a substitution adjacent to an acylated cysteine disabled virus replication. In contrast, a conservative substitution at this position, other exchanges in TMR and CT and moving the TMR cysteine to the CT had only subtle effects on virus growth. Yet, some of the mutated codons reverted to the original or other amino acids. Recombinant viruses were propagated in MDCK cells and embryonated chicken eggs and analyzed by mass spectrometry. No under-acylated peptides were detected, even the two lethal mutations did not abolish acylation. Point mutations only moderately affected the stearate content, while relocating the TMR cysteine to the CT virtually eliminated attachment of stearate. More stearate was attached if human viruses were grown in mammalian compared to avian cells. Hence, the location of an acylation site relative to the TMR represents the principal signal for stearate attachment, while the sequence context and the cell type modulate the fatty acid pattern.
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Rezvani, Reza. « Evaluation of acylation stimulating protein (ASP) and adipokines in relationship with determinants of obesity and its consequences ». Doctoral thesis, Université Laval, 2014. http://hdl.handle.net/20.500.11794/25252.
Texte intégralRésumé :
L’obésité est associée avec plusieurs désordres métaboliques d’envergure dont le diabète, les maladies cardiovasculaires et la stéatose hépatique. De nouvelles études visant le développement des traitements efficaces contre l’obésité et ses complications ont été entreprises afin d’élucider les mécanismes pathophysiologiques par lesquels l’obésité induit ou amplifie ses conséquences négatives. Le tissu adipeux sécrète plusieurs hormones ou adipokines qui sont impliquées dans la régulation du poids corporel ainsi que l’homéostasie métabolique. La protéine stimulant l’acylation (ASP) est une adipokine stimulant la synthèse des triglycérides et leur stockage au niveau du tissu adipeux (et ceci, en agissant à travers son récepteur : le C5L2). Cette thèse se penche sur diverses populations humaines et évalue les changements au niveau de différentes adipokines, plus particulièrement l’ASP, en lien avec les facteurs déterminants de l’obésité. Cet objectif global s’est concrétisé à travers quatre études : I) L’évaluation des niveaux d’adipokines chez des patients consommant des breuvages édulcorés au glucose ou au fructose afin de déterminer les effets de la composition de la diète sur la fonction du tissu adipeux, II) Une étude transversale évaluant le lien entre l’ASP et les facteurs de risque cardiométabolique dans une population à risque, III) une étude chez des femmes souffrant d’obésité sévère qui ont subi une chirurgie bariatrique, afin de déterminer les associations entre l’expression hépatique des récepteurs liés au facteur du complément C3 avec les niveaux d’hormones sexuelles et d’adipokines post-chirurgie, et IV) l’évaluation des niveaux sanguins d’adipokines ainsi que de l’expression du C3 et des récepteurs qui y sont reliés dans les tissus adipeux viscéral vs sous-cutané en lien avec le syndrome métabolique, les hormones sexuelles et le profil métabolique. Nous avons démontré que l’ASP et son récepteur offraient différentes réponses en fonction du sexe, de la présence d’un désordre métabolique, des niveaux d’hormones sexuelles, de l’organe impliqué ainsi que de la composition de la diète : tous des facteurs déterminants pour l’obésité. En conclusion, ces résultats suggèrent que l’ASP agit comme médiateur entre les facteurs exogènes et les évènements biologiques menant à l’obésité et ses conséquences métaboliques.Obesity is associated with many major metabolic disorders, especially diabetes, cardiovascular disorders and fatty liver disease. Aimed at developing effective therapies for obesity and its complications, new research has intensified to elucidate the pathophysiological mechanisms by which obesity induces or amplifies its major adverse consequences. Adipose tissue, as an endocrine organ, secretes several hormones termed “adipokines” that are involved in energy homeostasis and weight regulation. Dysfunction of adipokine pathways has been recognized as a key etiological factor of obesity-induced disorders. Acylation stimulating protein (ASP) is an adipokine that stimulates triglyceride synthesis and storage in adipose tissue by enhancing glucose and fatty acid uptake. ASP acts via its receptor C5L2. This thesis investigates several human populations under varying external and internal conditions and evaluates changes in adipokines, in particular ASP and its related proteins, in association with obesity determinants. This overall aim is achieved through four studies including the following: I) evaluation of adipokines in healthy overweight/obese adults consuming glucose- or fructose-sweetened beverages to determine the effects of diet composition on adipose tissue function II) a cross-sectional population-based study to determine fasting serum ASP and its relationships with cardiometabolic risk factors in a relatively high risk adult population III) a study on severely-obese pre/post-menopausal women, who underwent bariatric surgery, to determine associations of hepatic gene expression of complement C3 related receptors, sex hormones, adipokines and metabolic profiles as well as evaluating obesity improvement after surgery IV) a study on women with a wide age and BMI range to determine plasma adipokine levels and adipose tissue depot gene expression of C3 and related receptors in association with metabolic syndrome criteria, ovarian hormones and metabolic profile. I found different responses of ASP and its receptor according to gender, metabolic disorder, sex hormone levels, organ involvement and diet composition: all factors critical as obesity determinants. The results presented here demonstrate that ASP may mediate the link between obesity-related exogenous factors and biologic events that lead to obesity consequences. In conclusion, these findings validate that obesity is a low-grade inflammatory status with multi-organ involvement, evidencing sex differences and dynamic interactions between immune and metabolic response determinants.
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Banks, Courtney Jean. « Post-Translational Regulation of Superoxide Dismutase 1 (SOD1) : The Effect of K122 Acylation on SOD1's Metabolic Activity ». BYU ScholarsArchive, 2017. https://scholarsarchive.byu.edu/etd/6941.
Texte intégralRésumé :
Many mutations in superoxide dismutase 1 (SOD1) cause destabilization and misfolding of the protein and are implicated in amyotrophic lateral sclerosis. Likewise, a few post-translational modifications (PTMs) on SOD1 have been shown to cause the same phenotype. However, relatively few PTMs on SOD1 have been studied in depth and, in particular, very few studies have demonstrated how these PTMs affect SOD1's various biological roles. SOD1 is traditionally known for its role in reactive oxygen species (ROS)-scavenging but has also been found to have a few other biological roles, including transcription factor activity to promote genomic stability, preservation of cytoskeletal activity, maintaining zinc and copper homeostasis, and suppressing respiration. We have used the computational analysis tool, SAPH-ire, to find PTM 'hotspots' on SOD1 that have a high likelihood of affecting its biological functions. Interestingly, the top seven ranked PTM 'hotspots' were found in a small region of SOD1, between S98-K128. We focused our studies on one of the PTM 'hotspots' found in this region, lysine-122 (K122). K122 is found in the electrostatic loop of SOD1, a loop that is important for shuttling in superoxide radicals to be neutralized. According to our data, and other studies, this lysine is both succinylated and acetylated. We found that acetyl and succinyl-mimetics (K122Q and K122E, respectively) of this site do not affect its ROS scavenging activity but do prevent SOD1 from suppressing respiration and decrease its localization to the mitochondria. Further, when cells are depleted of SIRT5 (the desuccinylase for K122), SOD1 can no longer suppress respiration. Additionally, we found that SOD1 appears to suppress respiration at complex I, whether directly or through an indirect pathway is unknown. When HCT116 colon cancer cells were depleted of endogenous SOD1, the overexpressed succinyl K122-mimetic (K122E) could not recover growth as well as overexpressed WT SOD1. The K122E SOD1 expressing cells also exhibited increased mitochondrial ROS and unhealthier mitochondria. We propose a mechanism whereby SOD1 suppression of respiration acts as an additional regulator of oxidative stress: SOD1 suppresses the electron transport chain to decrease reactive oxygen species leakage and to promote healthier mitochondria and growth.
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Konrad, Sebastian [Verfasser], et Thomas [Akademischer Betreuer] Ott. « The plasma membrane attachment of Remorin microdomain marker proteins is stabilized by S-acylation / Sebastian Konrad ; Betreuer : Thomas Ott ». München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2015. http://d-nb.info/1119706033/34.
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Brett, Katharina [Verfasser], Michael [Akademischer Betreuer] Veit, Alexander [Akademischer Betreuer] Herrmann et Alexey [Akademischer Betreuer] Zaikin. « Molecular requirements of influenza virus hemagglutinin for site-specific S-acylation and virus replication / Katharina Brett. Gutachter : Michael Veit ; Alexander Herrmann ; Alexey Zaikin ». Berlin : Lebenswissenschaftliche Fakultät, 2015. http://d-nb.info/1075541255/34.
Texte intégral
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Hamel, Laura Dawn. « Targeting Autopalmitoylation to Modulate Protein S-Palmitoylation ». Scholar Commons, 2015. http://scholarcommons.usf.edu/etd/5960.
Texte intégralRésumé :
Palmitoylation refers to the covalent attachment of fatty acids, such as palmitate, onto the cysteine residues of proteins. This process may subsequently alter their localization and function. Nearly all of the enzymes that catalyze palmitoylation, zDHHC protein acyl transferases (PATs), are implicated in neurological disorders, infectious diseases, and cancer in humans. Of particular interest to those who study palmitoylation are Ras family GTPas and zDHHC9-GCP16, the zDHHC PAT that palmitoylates Ras proteins. Erf2-Erf4 is the zDHHC PAT that palmitoylates Ras proteins in Saccharomyces cerevisiae. Currently, there are no methods to therapeutically target palmitoylation for the treatment of disease. One of the barriers to identifying a modulator of palmitoylation is the lack of a reliable high-throughput screening system. To date, few assay systems have been developed to examine the kinetics and mechanism of that palmitoylation reaction. This lab has developed a fluorescence-based coupled assay to gain insight into the enzymology, biochemical mechanism, and kinetics of the palmitoylation reaction. This assay may be used to identify specific inhibitors of autopalmitoylation. In the first step of this reaction, the palmitoyl-moiety from palmitoyl-CoA is transferred to the zDHHC9 PAT cysteine side chain to form a palmitoyl:enzyme intermediate. The second step of palmitoylation is the subsequent transfer of the palmitoyl-moiety from the palmitoyl:enzyme intermediate to the cysteine residue of the substrate protein. This fluorescence-based coupled assay was utilized to screen a natural products library and a unique synthetic compound library for inhibitors of Erf2 autopalmitoylation. These screens led to the identification of fungal metabolite extracts and ten bis-cyclic piperazine compounds that inhibit Erf2 autopalmitoylation in the low micromolar range. This effect is similar to known inhibitors of palmitoylation that lack specificity for the palmitoylation reaction itself.
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Yogesh, S. « Design and Development of Metal-free Cross Dehydrogenative Coupling Reactions for the Construction of C-S, C-O and C-C bonds ». Thesis, 2017. http://etd.iisc.ac.in/handle/2005/3698.
Texte intégralRésumé :
The thesis entitled “Design and Development of Metal-Free Cross Dehydrogenative Coupling Reactions for the construction of C-S, C-O and C-C bonds” is divided into three Chapters. Chapter 1 is presented in five parts, which reveals the cross dehydrogenative coupling (CDC) strategies for the C–S bond forming reactions through C–H functionalization strategy using heterocyclic thiols and thiones. Chapter 2 presents tetrabutyl ammonium iodide (TBAI) catalyzed chemoselective α-aminoxylation of ketones with N-hydroxyimidates using TBHP as oxidant under cross dehydrogenative coupling (CDC) strategy. Chapter 3 describes a transition metal-free Minisci reaction for the acylation of isoquinolines, quinolines, and quinoxaline.
Chapter 1
Iodine Promoted C-S Bond Forming Reactions using Dimethyl Sulfoxide as an Oxidant
Chapter 1 reveals the utility of cross dehydrogenative coupling (CDC) reactions for the formation of C–S bonds by employing C–H functionalization strategies.1 The direct functionalization of C–H bonds to form C–C and C–X (N, O, S and P) bonds using metal-free reaction conditions is an interesting research topic in recent years.2 Use of dimethyl sulfoxide as an oxidant is emerging as one of the research topics of great interest and utility.3 Heterocyclic thiols and thiones are important precursors for synthesizing a variety of pharmaceuticals and biologically active compounds.4 Therefore it is useful to develop CDC reactions using heterocyclic thiols and thiones as precursors. In this chapter, we describe CDC reactions of heterocyclic thiols and thiones for the sulfenylation of ketones, aldehydes, α, β unsaturated methyl ketone derivatives, pyrazolones, enaminones and imidazoheterocycles using DMSO as an oxidant
Chapter 1: Part 1
Iodine Promoted Regioselective α-Sulfenylation of Carbonyl Compounds using Dimethyl Sulfoxide as an Oxidant: In this chapter, a rare regioselective C–H sulfenylation of carbonyl compounds with heterocyclic thiones and thiols have been described using iodine and dimethyl sulfoxide as reagents. Thus, dimethyl sulfoxide (as an oxidant) and stoichiometric amount of iodine have been used for the sulfenylation of ketones using heterocyclic thiones. Whereas the sulfenylation of ketones with heterocyclic thiols required catalytic amount of iodine. This protocol offers a rare regioselective sulfenylation of (i) methyl ketones in the presence of more reactive α-CH2 or α-CH groups, and (ii) aldehydes under CDC method. A few representative examples are highlighted in Scheme 1.5 The application of this methodology has been demonstrated by synthesizing a few precursors for Julia-Kocienski olefination intermediates.
Scheme 1. Iodine promoted rare regioselective α-sulfenylation of ketones and aldehydes
Siddaraj , Y.; Prabhu, K. R. Org. Lett. 2016, 18, 6090
Chapter 1: Part 2
Regioselective Sulfenylation of α’-CH3 or α’-CH2 Groups of α, β Unsaturated Ketones using
Dimethyl Sulfoxide as an Oxidant: In this chapter, an interesting regioselective sulfenylation of α’-CH3 or α’-CH2 groups of α, β unsaturated ketones using dimethyl sulfoxide as an oxidant and catalytic amount of aq. HI (20 mol %) as an additive has been described. This eco-friendly method uses readily available, inexpensive I2 or HI and DMSO. This methodology exhibits a high regioselectivity without forming Michael addition product in the presence of strong acid such as aq. HI or iodine, which is difficult to achieve under cross dehydrogenative coupling (CDC) conditions. Current methodology exhibits a broad substrate scope. A few examples are shown in Scheme 2.6
Scheme 2. HI and DMSO promoted α’-sulfenylation of α, β unsaturated ketones
Siddaraju, Y.; Prabhu, K. R. (Manuscript submitted)
Chapter 1: Part 3
Iodine Catalyzed Sulfenylation of Pyrazolones using Dimethyl Sulfoxide as an Oxidant: In this chapter, a sustainable and efficient strategy for the sulfenylation of pyrazolones has been described using metal-free conditions by employing DMSO as an oxidant and iodine as a catalyst. A variety of heterocyclic thiols, heterocyclic thiones and disulfides undergo C–H functionalization reaction with pyrazolone derivatives furnishing the corresponding sulfenylated products in short time. Most of the products are isolated in pure form without column purification. A few examples are presented in Scheme 3.7
Scheme 3. Iodine promoted sulfenylation of pyrazolones
Siddaraju, Y.; Prabhu, K. R. Org. Biomol. Chem. 2017, 15, 5191
Chapter 1: Part 4
Iodine-Catalyzed Cross Dehydrogenative Coupling Reaction: Sulfenylation of Enaminones using Dimethyl Sulfoxide as an Oxidant: In this chapter, synthesis of poly functionalized aminothioalkenes has been described using substoichiometric amount of iodine and DMSO as an oxidant. This metal-free methodology enables a facile sulfenylation of enaminones with heterocyclic thiols and thiones. This methodology is one of the simple approaches for the sulfenylation of enaminones under cross dehydrogenative coupling method. A few examples are highlighted in Scheme 4.8
Scheme 4. Cross-dehydrogenative coupling approach for sulfenylation of enaminones
Siddaraju, Y.; Prabhu, K. R. J. Org. Chem. 2017, 82, 3084
Chapter 1: Part 5
Iodine-Catalyzed Cross Dehydrogenative Coupling Reaction: A Regioselective Sulfenylation of Imidazoheterocycles using DMSO as an Oxidant: In this chapter, a simple synthetic approach for the regioselective sulfenylation of imidazoheterocycles using iodine as a catalyst and DMSO as an oxidant under cross dehydrogenative coupling (CDC) reaction conditions has been demonstrated. This protocol provides an efficient, mild and inexpensive method for coupling heterocyclic thiols and heterocyclic thiones with imidazoheterocycles. This is the first report on sulfenylation of imidazoheterocycles with heterocyclic thiols and heterocyclic thiones under metal-free conditions. A few examples are shown in Scheme 5.9
Scheme 5. Cross-dehydrogenative coupling approach for sulfenylation of imidazoheterocycles
Siddaraju, Y.; Prabhu, K. R. J. Org. Chem. 2016, 81, 7838
Chapter 2
Chemoselective α-Aminoxylation of Aryl Ketones: Cross Dehydrogenative Coupling Reactions Catalyzed by Tetrabutyl Ammonium Iodide: In this chapter, chemoselective α-aminoxylation of ketones with N-hydroxyimidates catalyzed by tetrabutyl ammonium iodide (TBAI) has been presented. The coupling reaction of a variety of ketones with N-hydroxysuccinimide (NHSI), N-hydroxyphthalimide (NHPI), N-hydroxybenzotriazole (HOBt) or 1-hydroxy-7-azabenzotriazole (HOAt) using TBHP as oxidant has been investigated. This α-aminoxylation of ketones is chemoselective as aryl methyl ketones, aliphatic ketones as well as benzylic position are inactive under the reaction condition. A few examples are highlighted in Scheme 6.10 The application of this method has been demonstrated by transforming a few coupled products into synthetically useful vinyl phosphates.
Scheme 6. Chemoselective α-aminoxylation of ketones with N-hydroxyimidates
Siddaraju, Y.; Prabhu, K. R. Org. Biomol. Chem. 2015, 13, 11651
Chapter 3
A Transition Metal-Free Minisci Reaction: Acylation of Isoquinolines, Quinolines, and Quinoxaline: In this chapter, transition metal-free acylation of isoquinoline, quinoline and quinoxaline derivatives with aldehydes has been described by employing TBAB (tetrabutyl ammonium bromide, 30 mol %) and K2S2O8 as an oxidant under cross dehydrogenative coupling (CDC) reaction. This intermolecular acylation of electron-deficient heteroarenes provides an easy access and a novel acylation method of heterocyclic compounds. The application of this CDC strategy has been illustrated by synthesizing isoquinoline-derived natural products. A few representative examples are shown in Scheme 7.11
Scheme 7. CDC reactions of heteroarenes with aldehydes
Siddaraju, Y.; Lamani, M.; Prabhu, K. R. J. Org. Chem. 2014, 79, 3856
Chapitres de livres sur le sujet "S-Acylation"
1
Kordyukova, Larisa, Ludwig Krabben, Marina Serebryakova et Michael Veit. « S-Acylation of Proteins ». Dans Post-Translational Modification of Proteins, 265–91. New York, NY : Springer New York, 2019. http://dx.doi.org/10.1007/978-1-4939-9055-9_17.
Texte intégral
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Hemsley, Piers A. « Assaying Protein S-Acylation in Plants ». Dans Methods in Molecular Biology, 141–46. Totowa, NJ : Humana Press, 2013. http://dx.doi.org/10.1007/978-1-62703-532-3_15.
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Greaves, Jennifer, et Nicholas C. O. Tomkinson. « Detection of Heterogeneous Protein S-Acylation in Cells ». Dans Methods in Molecular Biology, 13–33. New York, NY : Springer New York, 2019. http://dx.doi.org/10.1007/978-1-4939-9532-5_2.
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Ji, Yuhuan, et Cheng Lin. « Direct Analysis of Protein S-Acylation by Mass Spectrometry ». Dans Methods in Molecular Biology, 59–70. New York, NY : Springer New York, 2019. http://dx.doi.org/10.1007/978-1-4939-9532-5_5.
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Hurst, Charlotte H., Dionne Turnbull et Piers A. Hemsley. « Determination of Protein S-Acylation State by Enhanced Acyl-Switch Methods ». Dans Methods in Molecular Biology, 3–11. New York, NY : Springer New York, 2019. http://dx.doi.org/10.1007/978-1-4939-9532-5_1.
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Sorek, Nadav, Amir Akerman et Shaul Yalovsky. « Analysis of Protein Prenylation and S-Acylation Using Gas Chromatography–Coupled Mass Spectrometry ». Dans Methods in Molecular Biology, 121–34. Totowa, NJ : Humana Press, 2013. http://dx.doi.org/10.1007/978-1-62703-532-3_13.
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Woodley, Keith T., et Mark O. Collins. « Quantitative Analysis of Protein S-Acylation Site Dynamics Using Site-Specific Acyl-Biotin Exchange (ssABE) ». Dans Methods in Molecular Biology, 71–82. New York, NY : Springer New York, 2019. http://dx.doi.org/10.1007/978-1-4939-9232-4_6.
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Rudorf, W. D. « S-Acylation of Thiopyranthiones ». Dans Six-Membered Hetarenes with One Chalcogen, 1. Georg Thieme Verlag KG, 2003. http://dx.doi.org/10.1055/sos-sd-014-00810.
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Rudorf, W. D. « By S-Alkylation or S-Acylation ». Dans Six-Membered Hetarenes with One Chalcogen, 1. Georg Thieme Verlag KG, 2003. http://dx.doi.org/10.1055/sos-sd-014-00808.
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Spitzner, D. « S-Alkylation or S-Acylation of N-Substituted Pyridinethiones ». Dans Six-Membered Hetarenes with One Nitrogen or Phosphorus Atom, 1. Georg Thieme Verlag KG, 2005. http://dx.doi.org/10.1055/sos-sd-015-00524.
Texte intégralActes de conférences sur le sujet "S-Acylation"
1
Zapata-Romero, Gilberto A., Markus Doerr et Martha C. Daza. « Lipase-catalyzed O-acylation of (RS)-propranolol is determined by the acyl group length ». Dans VIII Simpósio de Estrutura Eletrônica e Dinâmica Molecular. Universidade de Brasília, 2020. http://dx.doi.org/10.21826/viiiseedmol2020130.
Texte intégralRésumé :
We employed a computational modeling approach to study the Michaelis complexes of (R)- and (S)-propranolol with serine-acylated Candida antarctica lipase B using four acyl groups: ethanoyl, butanoyl, octanoyl and hexadecanoyl. Our methodology involves sampling Michaelis complex conformations, first through ensemble docking using consensus scoring, and second by molecular dynamics simulations employing a quantum mechanics/molecular mechanics approach. The conformations are then categorized into two classes of near attack conformations, according to the distance of (a) the amino and (b) the hydroxy group of propranolol to the catalytic residues. The relative populations of these two classes of conformations was found to be consistent with the experimentally-observed exclusive chemoselectivity toward O-acylation with ethanoyl. Furthermore, we predict that increasing the length of the hydrocarbon chain of the acyl group will cause O-acylation to be unfavorable.
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Makowiec, Sławomir, Janusz Rachoń, Natalia Pawelska, Paweł Punda et Karolina Janikowska. « TMSCl Promoted Acylation of Amines with 5-(α-amino- α\'-hydroxy)methylene Meldrum\'s Acids – Elucidation of Mechanism. » Dans The 15th International Electronic Conference on Synthetic Organic Chemistry. Basel, Switzerland : MDPI, 2011. http://dx.doi.org/10.3390/ecsoc-15-00632.
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Zapata-Romero, Gilberto A., Markus Doerr et Martha C. Daza. « Enantioselective lipase-catalyzed O-acylation of (RS)-propranolol : analysis of the hydrogen bonds essential for catalysis ». Dans VIII Simpósio de Estrutura Eletrônica e Dinâmica Molecular. Universidade de Brasília, 2020. http://dx.doi.org/10.21826/viiiseedmol2020131.
Texte intégralRésumé :
We investigated the effect of the acyl group size in the enantioselectivity of the acylation of propranolol, an amino alcohol used as β-adrenergic blocking agent. We applied a methodology frequently used to model enantioselectivity that is based on the hydrogen bonds present in the tetrahedral intermediate, which occurs in lipase-catalyzed reactions. We sampled the conformations of the tetrahedral intermediate corresponding to the esterification of both enantiomers of propranolol with ethanoyl and butanoyl, employing molecular dynamics simulation together with a quantum mechanics/molecular mechanics approach. We found that the population of these hydrogen bonds provides insight into the mechanism of the reaction. However, they are not conclusive about the role of the acyl group in the enantioselectivity. For both acyl groups, we found that the reaction from the Michaelis complex to the tetrahedral intermediate is more favorable for (R)-propranolol and the reaction from the tetrahedral intermediate to the enzyme/product complex is more favorable for (S)-propranolol.
4
Fears, R., H. Ferres et R. Standring. « THE PROTECTIVE EFFECT OF ACYLATI0N ON THE STABILITY OF EMINASE (APSAC) IN HUMAN PLASMA ». Dans XIth International Congress on Thrombosis and Haemostasis. Schattauer GmbH, 1987. http://dx.doi.org/10.1055/s-0038-1642999.
Texte intégralRésumé :
Clinical and animal studies indicate that APSAC (anisoylated plasminogen.streptokinase activator complex, Eminase) circulates longer in the bloodstream in an active form than the other thrombolytics. In the present studies in vitro u/e have found that functional activity of APSAC is maintained in human plasma longer than that of SK.plasmin(ogen): the relative stability half-lives are similar to the plasma clearance haif-lives in patients. Some of the loss of activity of SK at early times can be attributed to neutralisation by inhibitors. Thus, the survival of fibrinolytically-active SK was promoted in plasma depleted in α2-antiplasmin (α2AP) and α2AP-SK.plasmin complexes (detected by immunoblotting) formed rapidly in normal plasma. Corresponding studies with α2 macroglobulin-depleted plasma suggested a slight, late influence on SK activity but the inhibitor complex has not been detected unequivocally. In addition, loss of SK activity can be attributed, in part, to. rapid degradation to low molecular products. The degradation of SK in APSAC was much slower. In other comparative studies, the stability of APSAC was found to be similar to the stability of prourokinase and much superior to that of SK which is similar to UK; t-PA is intermediate in stability.Maintenance of fibrinolytic activity vivo depends on the stability of the thrombolytic, its rate of clearance and mode of administration. The protective effect of acylation, demonstrated in these experiments, explains why the objective of maintaining a high level of fibrinolytic activity after intravenous bolus injection of APSAC is less compromised by opposing inactivation processes.
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Purdon, A. D., et J. B. Smith. « RELEASE AND TRANSACYLATION OF ARACHIDONATE FROM A COMMON POOL OF 1-ACYL-2-ARACHIDONOYL GLYCEROPHOSPHOCHOLINE IN HUMAN PLATELETS ». Dans XIth International Congress on Thrombosis and Haemostasis. Schattauer GmbH, 1987. http://dx.doi.org/10.1055/s-0038-1643391.
Texte intégralRésumé :
We have previously shown that the main source of arachidonate in thrombin-stimulated human platelets is 1-acyl-2-arachidonoyl (AA) glycerophosphocholine (GPC) and release of 3H-AA from this phospholipid also was correlated with increased 3H-AA in ether phospholipid. This ATP independent transfer of 3H-AA from 1,2 diacyl GPC to ether phospholipid (transacylation) also occurs in resting cells. Human platelets in 1/10 volume of plasma (ACD anticoagulant, pH 6.5) were radiolabelled with 3H-AA for 60 min at 37°C and then exogenous 3H-AA was removed by gel filtration into Tyrode's buffer, pH 7.4, 0.2% albumin. These radiolabelled cells were incubated in the absence of exogenous 3H-AA for four hours followed by Bligh and Dyer extraction and thin layer chromatography purification of phospholipids. 3H-AA in 1,2 diacyl GPC was found to decrease by over 20% and increase substantially in 1-0-alkyl-2-acyl GPC and 1-0-alk-1'-enyl-2-acyl glycerophospho ethanolamine (GPE), In this same time interval the mass of AA released by thrombin (5 U/ml, 10 min, 37°C, no stirring)in the presence of BIT 775C and measured by GLC, stayed the same (30 nmoles/109 cells), however, the specific activity decreased. Using reverse phase HPLC to resolve diradylglycerobenzoate derivatives of phospholipids: acylation, deacylation, and transacylation were observed for individual AA-containing molecular species of phospholipid, including those with an unsaturated fatty acid at sn-1. In particular the radiolabellinq of the 1-unsaturate-2-arachidonoyl GPC correlated with the specific activity of the 3H-AA released by stimulation with thrombin. Furthermore, 1-arachidonoyl-2-3H-arachidonoyl GPC was completely deacylated while 50 % of its mass remained. This contrasted with 16:0, and 18:0-2-arachidonoyl GPC in which the specific activity remained the same before and after deacylation. We conclude that deacylation of AA-containing molecular species of 1,2 diacyl GPC in stimulated cells includes molecular species which are also a source of arachidonic acid for transacylation reactions.