Purification and properties of gamma-glutamyl transpeptidase from rat deciduoma

gamma-Glutamyl transpeptidase has been purified by chromatographic methods from endometrium of rat deciduoma. The membrane-bound enzyme, digested with papain, eluted as a single fraction during chromatography and the final preparation had a specific activity of 104.5 U/mg protein. The molecular weight of the native enzyme was approximately 70,000 and the protein could be resolved into a heavy and a light fraction on sodium dodecyl sulfate-acrylamide gel electrophoresis with molecular weights of 45,000 and 23,000, respectively. The enzyme had a pH optimum of 8.2 and Km's for donor (p-nitroanilide) and acceptor (glycylglycine) were 1 and 7.6 mM, respectively. The enzyme was inhibited by L-serine in the presence of borate with a Ki of 22 microM. The decidual enzyme was not heat stable and its electrophoretic mobility was decreased after neuraminidase treatment.