The enzyme, found in vertebrates, has no activity toward α-(γ-L-glutamyl)-L-amino acids (cf. EC 184.108.40.206, γ-glutamylcyclotransferase). The enzyme acts as a cyclotransferase, cleaving the amide bond via transamidation using the α-amine of the γ-L-glutamyl residue, releasing it as the cyclic 5-oxo-L-proline.
Fink, M.L., Chung, S.I. and Folk, J.E. γ-Glutamylamine cyclotransferase: specificity toward ε-(L-γ-glutamyl)-L-lysine and related compounds. Proc. Natl Acad. Sci. USA77 (1980) 4564–4568. [DOI] [PMID: 6107907]
Oakley, A.J., Coggan, M. and Board, P.G. Identification and characterization of γ-glutamylamine cyclotransferase, an enzyme responsible for γ-glutamyl-ε-lysine catabolism. J. Biol. Chem.285 (2010) 9642–9648. [DOI] [PMID: 20110353]