1 GSSG is a tripeptide that contains an unusual peptide linkage between the amine group of cysteine (which is attached by normal
peptide linkage to a glycine) and the carboxyl group of the glutamate side-chain. It is an antioxidant, preventing damage to
important cellular components caused by reactive oxygen species such as free radicals and peroxides.
2 Thiol groups are reducing agents, existing at a concentration of approximately 5 mM in animal cells.Glutathione reduces
disulfide bondsformed within cytoplasmic proteins to cysteines by serving as an electron donor.In the process, glutathione is
converted to its oxidized form glutathione disulfide (GSSG), also called L(-)-Glutathione.
3 GSSG is found almost exclusively in its reduced form, since the enzyme that reverts it from its oxidized form,glutathione
reductase, is constitutively active and inducible upon oxidative stress.In fact, the ratio of reduced glutathione to oxidized
glutathione within cells is often used as a measure of cellular toxicity.