Glutathione (GSH) is an antioxidant in plants, animals, fungi, and some bacteria and archaea. Glutathione is capable of preventing damage to important cellular components caused by reactive oxygen species such as free radicals, peroxides, lipid peroxides, and heavy metals.It is a tripeptide with a gamma peptide linkage between the carboxyl group of the glutamate side chain and cysteine. The carboxyl group of the cysteine residue is attached by normal peptide linkage to glycine.

Occurrence

Glutathione is the most abundant thiol in animal cells, ranging from 0.5 to 10 mM. It is present in the cytosol and the organelles.Human beings synthesize glutathione, but a few eukaryotes do not, including Fabaceae, Entamoeba, and Giardia. The only known archaea that make glutathione are halobacteria. Some bacteria, such as cyanobacteria and proteobacteria, can biosynthesize glutathione.

Biochemical function

Glutathione exists in reduced (GSH) and oxidized (GSSG) states. The ratio of reduced glutathione to oxidized glutathione within cells is a measure of cellular oxidative stress where increased GSSG-to-GSH ratio is indicative of greater oxidative stress. In healthy cells and tissue, more than 90% of the total glutathione pool is in the reduced form (GSH), with the remainder in the disulfide form (GSSG).In the reduced state, the thiol group of cysteinyl residue is a source of one reducing equivalent. Glutathione disulfide (GSSG) is thereby generated. The oxidized state is converted to the reduced state by NADPH.This conversion is catalyzed by glutathione reductase:NADPH + GSSG + H2O → 2 GSH + NADP+ + OH−

Uses

Winemaking

The content of glutathione in must, the first raw form of wine, determines the browning, or caramelizing effect, during the production of white wine by trapping the caffeoyltartaric acid quinones generated by enzymic oxidation as grape reaction product.Its concentration in wine can be determined by UPLC-MRM mass spectrometry.

Cosmetics

Glutathione is the most common agent taken by mouth in an attempt to whiten the skin.It may also be used as a cream.Whether or not it actually works is unclear as of 2019.Due to side effects that may result with intravenous use, the government of the Philippines recommends against such use.