Glutathion

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Glutathion

Glutathione (GSH) is a peptide molecule synthesized in the body from the amino acids L-glutamic acid, L-cysteine and glycine. The peptide is an antioxidant, preventing damage to important cellular components caused by reactive oxygen species such as free radicals and peroxides.

Structure and properties

Glutathione is a tripeptide with a gamma peptide linkage between the carboxyl group of the glutamate side chain and the amine group of cysteine. The carboxyl group of the cysteine residue is attached by normal peptide linkage to glycine. Its chemical structure is HO2CCH(NH2)CH2C(=O)NHCH(C(=O)NH2)CH2CO2H.

Function

Glutathione exists in reduced (GSH) and oxidized (GSSG) states. In the reduced state, the thiol group of cysteine is able to donate a reducing equivalent (H++ e−) to other unstable molecules, such as reactive oxygen species. In donating an electron, glutathione itself becomes reactive, but readily reacts with another reactive glutathione to form glutathione disulfide (GSSG). In healthy cells and tissue, more than 90% of the total glutathione pool is in the reduced form (GSH) and less than 10% exists in the disulfide form (GSSG).

Biosynthesis

Glutathione is synthesized in the cytosol, in two adenosine triphosphate-dependent steps. First, gamma-glutamylcysteine is synthesized from L-glutamate and cysteine. This reaction is catalyzed by glutamate-cysteine ligase. Second, glycine is added to the C-terminal of gamma-glutamylcysteine. This reaction is catalyzed by glutathione synthetase.

Role in health and disease

Glutathione plays a crucial role in a multitude of biochemical reactions and is important for several processes, including DNA synthesis and repair, protein synthesis, prostaglandin synthesis, amino acid transport, and enzyme activation. Thus, every system in the body can be affected by the state of the glutathione system, especially the immune system, the nervous system, the gastrointestinal system, and the lungs.

See also

• Glutathione-ascorbate cycle
• Glutathione S-transferase
• Glutathione peroxidase