Gamma-glutamyltransferase-1 (GGT1; MIM 612346) is a membrane-bound extracellular enzyme that cleaves gamma-glutamyl peptide bonds in glutathione and other peptides and transfers the gamma-glutamyl moiety to acceptors. Autocatalytic cleavage of the GGT1 precursor polypeptide produces a heavy chain and a light chain that associate with each other to form the functional enzyme. Light chain-only GGTs, such as GGTLC2, contain a region corresponding to the GGT1 light chain, but they lack the membrane-anchoring heavy chain region (Heisterkamp et al., 2008 [PubMed 18357469]).[supplied by OMIM].