Glutathionylation is generally a reversible posttranslational modification that occurs to cysteine

Glutathionylation is generally a reversible posttranslational modification that occurs to cysteine residues that have been exposed to reactive oxygen species (P-SSG). toxicological pharmacological and oncological relevance. Here we compare reversible and irreversible glutathionylation. 1 INTRODUCTION Glutathione is usually a CAY10505 tripeptide (L-γ-glutamyl-L-cysteinyl-glycine Fig. 5.1) with multiple biological functions (Lushchak 2012 Meister & Anderson 1983 Sies 1999 It is an abundant low-molecular-mass thiol antioxidant which either interacts directly with reactive oxygen and nitrogen species (ROS and RNS respectively) or serves as a cofactor for many antioxidant and associated enzymes such as peroxidases and transferases (Foster Hess & Stamler 2009 In addition glutathione is (1) a storage form of cysteine; (2) a storage form and transporter of nitric oxide (as GSNO); (3) involved in the metabolism of estrogens leukotrienes and prostaglandins reduction of ribonucleotides to deoxyribonucleotides and maturation of iron-sulfur clusters of proteins; (4) involved in CAY10505 the regulation of certain transcription factors; and (5) involved in the detoxification of many endogenous compounds and xenobiotics (the mercapturate pathway). Glutathione also can be used even for the detoxification of ions of transition metals such as chromium (Giustarini et al. 2005 Holland & Avery 2011 Lushchak Kubrak Nykorak Storey & Lushchak 2008 Free glutathione exists mostly as two forms-reduced CAY10505 (GSH) and oxidized (glutathione disulfide; GSSG). Its biological activity is usually primarily related to the active thiol group of the cysteine residue. In the intracellular milieu glutathione is usually relatively stable due to the presence of an unusual γ-peptide bond between glutamate and cysteine residues. Intracellular peptidases specifically cleave peptide bonds formed from the α-carboxyl group but not from the γ-carboxyl group. Recent attention has been drawn to the importance of the glutathione pool that is utilized in the posttranslational modification of cysteine residues S-glutathionylation. Physique 5.1 Chemical structure of glutathione in reduced (A) and oxidized (disulfide) forms (B). Glutathione is usually synthesized in a two-step process catalyzed by the consecutive action of γ-glutamyl-L-cysteine ligase (γGLCL EC and glutathione synthetase (GLS EC The first enzyme in the pathway is generally considered to be a regulatory enzyme in the overall synthesis CAY10505 and is feedback-inhibited by glutathione (Richman & Meister 1975 Glutathione is usually consumed through reactions involving oxidation conjugation and hydrolysis. Oxidation can take place nonenzymatically through direct conversation with ROS and RNS and via enzymatic reactions catalyzed by glutathione-dependent peroxidases (Fig. 5.2). Diverse glutathione S-transferases (GSTs) catalyze conjugation of glutathione to endogenous and CAY10505 exogenous electrophiles. Finally a portion of the intracellular glutathi-one pool may be released to the extracellular environment in either reduced or oxidized forms (Fig. 5.2). Extracellular glutathione may be hydrolyzed by the ectoenzyme γ-L-glutamyl transpeptidase (GGT EC to cysteinylglycine which in turn may be hydrolyzed by dipeptidases to cysteine and glycine (Meister 1983 Cells can take up the products liberated by glutathione hydrolysis as individual amino acids or dipeptides. Thus a balance between production consumption hydrolysis and transport determines the concentrations of intra- and extracellular glutathione pools. These processes are finely Rabbit polyclonal to GALNT9. regulated and under normal conditions are well balanced. Regulation of glutathione levels occurs at the levels of transcription and translation and by posttranslational modifications of the enzymes involved in its synthesis (Lushchak 2012 Physique 5.2 Involvement of glutathione in the elimination of reactive oxygen and nitrogen species. Hydroxyl radical and nitric oxide (after oxidation to the NO+ form (nitrosyl cation)) or peroxynitrite (ONOO?) may interact directly with GSH leading to GSSG … Since glutathione plays a pivotal role as an antioxidant and participates in many regulatory and metabolic processes the glutathione biosynthetic pathway has attracted attention from pharmacologists and biomedical scientists as a possible target for medical interventions. These strategies are directed toward decreasing or increasing glutathione levels either at the.