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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.
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.
Glutamate cysteine ligase (GCL) catalyzes the first and rate-limiting step in the production of the cellular antioxidant glutathione (GSH), involving the ATP-dependent condensation of cysteine and glutamate to form the dipeptide gamma-glutamylcysteine (γ-GC). [5]
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:
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.
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.
The detoxification reactions comprise the first four steps of mercapturic acid synthesis, [19] with the conjugation to GSH serving to make the substrates more soluble and allowing them to be removed from the cell by transporters such as multidrug resistance-associated protein 1 . [8]