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Other names in common use include glutathione synthetase, and GSH synthetase. This enzyme participates in glutamate metabolism and glutathione metabolism . At least one compound, Phosphinate is known to inhibit this enzyme .
This reaction is the rate-limiting step in glutathione synthesis. [3] Second, glycine is added to the C-terminal of γ-glutamylcysteine. This condensation is catalyzed by glutathione synthetase. While all animal cells are capable of synthesizing glutathione, glutathione synthesis in the liver has been shown to be essential.
Glutamate–cysteine ligase (GCL) EC 6.3.2.2), previously known as γ-glutamylcysteine synthetase (GCS), is the first enzyme of the cellular glutathione (GSH) biosynthetic pathway that catalyzes the chemical reaction:
A second GSH molecule reduces the GS-SeR intermediate back to the selenol, releasing GS-SG as the by-product. A simplified representation is shown below: [5] RSeH + H 2 O 2 → RSeOH + H 2 O RSeOH + GSH → GS-SeR + H 2 O GS-SeR + GSH → GS-SG + RSeH. Glutathione reductase then reduces the oxidized glutathione to complete the cycle:
Glutathione reductase (GR) also known as glutathione-disulfide reductase (GSR) is an enzyme that in humans is encoded by the GSR gene.Glutathione reductase (EC 1.8.1.7) catalyzes the reduction of glutathione disulfide to the sulfhydryl form glutathione (), which is a critical molecule in resisting oxidative stress and maintaining the reducing environment of the cell.
The primary role of GSTs is to catalyze the conjugation of glutathione (GSH) with the electrophilic centers of a wide variety of molecules. The most commonly known substrates of GSTs are xenobiotic synthetic chemicals. There are also classes of GSTs that utilize glutathione as a cofactor rather than a substrate.
[13] [19] Specifically, the function of GSTs in this role is twofold: to bind both the substrate at the enzyme's hydrophobic H-site and GSH at the adjacent, hydrophilic G-site, which together form the active site of the enzyme; and subsequently to activate the thiol group of GSH, enabling the nucleophilic attack upon the substrate. [12]
The antioxidant enzyme glutathione peroxidase 4 (GPX4) belongs to the family of glutathione peroxidases, which consists of 8 known mammalian isoenzymes (GPX1–8).GPX4 catalyzes the reduction of hydrogen peroxide, organic hydroperoxides, and lipid peroxides at the expense of reduced glutathione and functions in the protection of cells against oxidative stress.