Total Glutathione in Whole Blood - Glutathione is a tripeptide formed by a peptide linkage between the amine group of cysteine linked to glycine and the carboxyl group of the glutamate side-chain. It is an abundant cellular reducing agent, whose major biological function is mitigating oxidative damage to biological macromolecules. Glutathione is also important in the metabolism and excretion of xenobiotic compounds.