Enzymic transpeptidation reactions involving γ-glutamyl peptides and α-amino-acyl peptides

Abstract

Two types of transpeptidation reaction, catalysed by different enzymes, were descr. These consisted in the transfer of the gamma- glutamyl and glycyl groups respectively, from linkage in a "donor" peptide to linkage with the amino group of a suitable acceptor. The gamma-glutamyl transpeptidase from kidney tissue was mainly studied. Reduced and oxidized glutathione, and 5 different synthetic gamma-glutamyl dipeptides acted as donors of the gamma-glutamyl group in the system. Thus the enzyme was relatively non-specific as regards the amino moiety of the donor peptide, and the same was true as regards the acceptor amino acid (or peptide). The glycyl transpeptidase was prepared from cabbage leaves. Various glycyl peptides were shown to act as donors of the glycyl group and, as in the gamma-glutamyl transpeptidase, the enzyme was relatively non-specific as regards the acceptor amino-acids. While the group transfer reactions resulting in the redistribution of gamma-glutamyl and glycyl groups, respectively, between donor peptides and various acceptors formed a prominent feature of the 2 systems, hydrolysis proceeded simultaneously. In the glycyl system hydrolysis was markedly inhibited by the presence of suitable acceptors.