Protéase à cystéine

Une protéase à cystéine, ou parfois protéase à thiol, est une peptidase dont le résidu d'acide aminé nucléophile de la triade (ou diade) catalytique est une cystéine. Comme toutes les peptidases, ces enzymes catalysent l'hydrolyse de certaines liaisons peptidiques de protéines. On trouve couramment de telles enzymes dans les fruits, par exemple la papaye, l'ananas, la figue et le kiwi, leur concentration tendant à être plus élevée lorsque le fruit n'est pas mûr ; on en trouve en fait plus généralement dans un grand nombre de plantes. Mécanisme catalytique La première étape du mécanisme réactionnel catalysé par les protéases à cystéine est la déprotonation du groupe thiol, porté par le résidu de cystéine du site actif, par la chaîne latérale basique d'un acide aminé voisin, généralement un résidu d'histidine. L'étape suivante est l'attaque nucléophile de l'atome de carbone constituant le carbonyle du substrat par l'anion sulfure de la cystéine déprotonée. Le fragment d

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Tuning and predicting biological affinity: aryl nitriles as cysteine protease inhibitors

Céline Freymond, Jose Enrico Quijano Quinsaat, Pablo Rivera Fuentes

A series of aryl nitrile-based ligands were prepd. to investigate the effect of their electrophilicity on the affinity against the cysteine proteases rhodesain and human cathepsin L. D. functional theory calcns. provided relative reactivities of the nitriles, enabling prediction of their biol. affinity and cytotoxicity and a clear structure-activity relationship.

2012

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Deficiency for the Cysteine Protease Cathepsin L Impairs Myc-Induced Tumorigenesis in a Mouse Model of Pancreatic Neuroendocrine Cancer

Nicola Rae Brindle, Douglas Hanahan, Ksenya Shchors

Motivated by the recent implication of cysteine protease cathepsin L as a potential target for anti-cancer drug development, we used a conditional MycER(TAM); Bcl-x(L) model of pancreatic neuroendocrine tumorigenesis (PNET) to assess the role of cathepsin L in Myc-induced tumor progression. By employing a cysteine cathepsin activity probe in vivo and in vitro, we first established that cathepsin activity increases during the initial stages of MycER(TAM); Bcl-x(L) tumor development. Among the cathepsin family members investigated, only cathepsin L was predominately produced by beta-tumor cells in neoplastic pancreata and, consistent with this, cathepsin L mRNA expression was rapidly upregulated following Myc activation in the beta cell compartment. By contrast, cathepsins B, S and C were highly enriched in tumor-infiltrating leukocytes. Genetic deletion of cathepsin L had no discernible effect on the initiation of neoplastic growth or concordant angiogenesis. However, the tumors that developed in the cathepsin L-deficient background were markedly reduced in size relative to their typical wild-type counterparts, indicative of a role for cathepsin L in enabling expansive tumor growth. Thus, genetic blockade of cathepsin L activity is inferred to retard Myc-driven tumor growth, encouraging the potential utility of pharmacological inhibitors of cysteine cathepsins in treating late stage tumors.

Public Library of Science2015

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Evolution of S-Cysteinylated and S-Glutathionylated Thiol Precursors during Oxidation of Melon B. and Sauvignon blanc Musts

Jérôme Vialaret

Thiol precursor content in Melon B. and Sauvignon blanc grape juices obtained under vacuum was determined by quantifying cysteinylated and glutathionylated conjugates of 3-mercaptohexan-1-ol (3MH) and 4-methyl-4-mercaptopentan-2-one (4MMP). This characterization allowed the study of thiol precursor evolution during ripening of Sauvignon blanc grapes in several viticultural situations together with grape reaction product (GRP) and the main substrate of polyphenoloxidase, that is, caftaric acid. Concentration of precursors greatly increased during ripening except for the cysteinylated conjugate of 4MMP. Precursor evolution was also monitored during the oxidation of grape juice. Addition of oxygen to a grape juice set off the enzymatic oxidation of hydroxycinnamic acids but did not negatively affect precursor concentrations. Part of the glutathionylated precursor of the 3MH was produced during prefermentative operations (up to 140% in Sauvignon blanc). Consequently, this precursor naturally occurring in grapes was also formed during prefermentative operations. The proportion of biogenetic and prefermentary formation of the glutathionylated precursor of 3MH was different under industrial conditions depending on the grape variety considered. Addition of glutathione and hexenal in grape juices of Melon B. and Sauvignon induced an increase of the production of 3MH and consequently of its acetate in the resulting wines. Residual glutathione in must has to be preserved to enhance the aromatic potential of grapes.

2010

Chargement

Peptidase

Les peptidases (ou protéases ou enzymes protéolytiques) sont des enzymes qui brisent les liaisons peptidiques des protéines. On parle alors de coupure protéolytique ou de protéolyse. Ce processus imp

Triade catalytique

redresse=1.5|vignette| Site actif de la protéase TEV (), une peptidase très sélective du virus de la gravure du tabac, montrant le substrat en noir et les résidus de la triade catalytique en rouge, ic

Protéolyse

En biochimie, la protéolyse est la segmentation des protéines en ses fragments de base (acides aminés) via l'hydrolyse catalysée par des enzymes dits « protéolytiques » (protéases ou hydrolases)

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