γ-glutamyl transferase is an enzyme that transfers gamma-glutamyl functional groups. It is found in many tissues, the most notable one being the liver, and has significance in medicine as a diagnostic marker. GGT catalyzes the transfer of the gamma-glutamyl moiety of glutathione to an acceptor that may be an amino acid, a peptide or water (forming glutamate). GGT plays a key role in the gamma-glutamyl cycle, a pathway for the synthesis and degradation of glutathione and drug and xenobiotic detoxification. Other lines of evidence indicate that GGT can also exert a prooxidant role, with regulatory effects at various levels in cellular signal transduction and cellular pathophysiology.http://www.creative-enzymes.com/product/Native-Human-GammaGlutamyl-Transferase_890.html