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Le glutathion est un pseudo-tripeptide formé par la condensation d'acide glutamique, de cystéine et de glycine : . Le glutathion, qui existe sous forme oxydée et réduite, intervient dans le maintien du potentiel redox du cytoplasme de la cellule. Il intervient aussi dans un certain nombre de réactions de détoxication et d'élimination d'espèces réactives de l'oxygène. À noter que le groupement amine de la cystéine se condense avec la fonction acide carboxylique en γ de l'acide glutamique. Pratiquement toutes les cellules en contiennent une concentration élevée. On le représente de manière simplifiée par GSH (forme réduite) ou GSSG (forme oxydée), la fonction thiol lui conférant ses principales propriétés biochimiques. Biosynthèse Sources naturelles Découvert en 1888, le glutathion, naturellement présent dans les plantes, les cellules animales et les champignons, est particulièrement concentré dans certains fruits (pamplemousses, pommes, oranges, pêches, bananes e

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Modulation of Subcellular Redox Homeostasis with Trialkylphosphines

Jade Noémie Nam Nguyen

Redox homeostasis is essential for cell function and its disruption is associated with multiple pathologies. Redox balance is largely regulated by the relative concentrations of reduced (GSH) and oxidized (GSSG) glutathione. In eukaryotic cells, this ratio is different in each cell compartment. There is a lack of chemical probes able to modulate GSH/GSSG to study the impact of redox stress in an organelle specific manner. Here, we highlight the importance of trialkylphosphines to induce reductive stress and how it can be targeted to a specific organelle. Our probe is selectively activated by endogenous nitroreductases, and releases tributylphosphine to trigger redox stress in mitochondria. Mechanistic studies revealed that the induced stress activates a cellular response orchestrated by transcription factor ATF4, which upregulates genes involved in glutathione catabolism.

SWISS CHEMICAL SOC2022

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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

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Disruption of mitochondrial redox homeostasis by enzymatic activation of a trialkylphosphine probe

Jade Noémie Nam Nguyen, Pablo Rivera Fuentes

Redox homeostasis is essential for cell function and its disruption is associated with multiple pathologies. Redox balance is largely regulated by the relative concentrations of reduced and oxidized glutathione. In eukaryotic cells, this ratio is different in each cell compartment, and disruption of the mitochondrial redox balance has been specifically linked to metabolic diseases. Here, we report a probe that is selectively activated by endogenous nitroreductases, and releases tributylphosphine to trigger redox stress in mitochondria. Mechanistic studies revealed that, counterintuitively, release of a reducing agent in mitochondria rapidly induced oxidative stress through accumulation of superoxide. This response is mediated by glutathione, suggesting a link between reductive and oxidative stress. Furthermore, mitochondrial redox stress activates a cellular response orchestrated by transcription factor ATF4, which upregulates genes involved in glutathione catabolism.

ROYAL SOC CHEMISTRY2021

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Antioxydant

vignette|300px|Modèle spatial de la molécule du glutathion. La sphère jaune représente l'atome réducteur de soufre qui apporte la fonction antioxydante. Les sphères rouges, bleues, blanches et grises

Métabolisme

Le métabolisme est l'ensemble des réactions chimiques qui se déroulent à l'intérieur de chaque cellule d'un être vivant et lui permettent notamment de se maintenir en vie, de se reproduire (se divis

Cystéine

La cystéine (abréviations IUPAC-IUBMB : Cys et C), du grec ancien (« vessie »), est un acide dont l'énantiomère L est l'un des aminés protéinogènes, encodé sur les ARN messagers par les codons UGU

BIO-212: Biological chemistry I

Biochemistry is a key discipline for the Life Sciences. Biological Chemistry I and II are two tightly interconnected courses that aim to describe and understand in molecular terms the processes that make life possible.

CH-313: Chemical biology

Closely interfacing with bioengineering and medicine, this course provides foundational concepts in applying small-molecule chemical toolsets to probe the functions of living systems at the mechanistic and molecular level with emphasis placed on quantitative understanding and improving human health.

CH-210: Biochemistry

Les constituants biochimiques de l'organisme, protéines, glucides, lipides, à la lumière de l'évolution des concepts et des progrès en biologie moléculaire et génétique, sont étudiés.