Mapping of the active site of rat kidney γ-glutamyl transpeptidase using activated esters and their amide derivatives Original Research Article

The enzyme γ-glutamyl transpeptidase (GGT), implicated in many physiological processes, catalyses the transfer of a γ-glutamyl from a donor substrate to an acyl acceptor substrate, usually an amino acid or a peptide. In order to investigate which moieties of the donor substrate are necessary for recognition by GGT, the structure of the well-recognized substrate l-γ-glutamyl-p-nitroanilide was modified. Several activated esters and their amide derivatives were synthesized and used as substrates. Kinetic (Km and Vmax) and inhibition constants (Ki) were measured and reveal that almost the entire γ-glutamyl moiety is necessary for recognition in the binding site of the donor substrate. The implied presence of certain complementary amino acids in this substrate binding site will allow the more rational design of various substrate analogues and inhibitors.