Glutathione is widely found in all forms of life and plays an essential role in the health of organisms, particularly aerobic organisms. In animals, including humans, and in plants, glutathione is the predominant non-protein thiol and functions as a redox buffer, keeping with its own SH groups those of proteins in a reduced condition, among other antioxidant activities.
Glutathione is present in tissues in concentrations as high as one millimolar. It plays roles in catalysis, metabolism, signal transduction, gene expression and apoptosis. It is a cofactor for glutathione S-transferases, enzymes which are involved in the detoxification of xenobiotics, including carcinogenic genotoxicants, and for the glutathione peroxidases, crucial selenium-containing antioxidant enzymes . It is also involved in the regeneration of ascorbate from its oxidized form, dehydroascorbate. There are undoubtedly roles of glutathione that are still to be discovered.