The Mechanism of the Formation of γ-Glutamylpeptides during<scp>l</scp>-Glutamic Acid Fermentation Contributed Solely by γ-Glutamyltranspeptidase

The enzyme of Corynebacterium glutamicum that catalyzes the formation of various γ-L(D)-glutamylpeptides by the reversal of hydrolysis was found to be γ-glutamyltranspeptidase. The enzyme catalyzed γ-l(d)-glutamyl transfer reaction from various γ-L(D)-glutamyl- peptides including glutathione. The susceptibility of D-isomers was 17% of that of l-isomers. Many kinds of α-l-amino acids and peptides such as γ-l-GIu-l-GIu could be γ-glutamyl acceptors. These findings offered full explanation on the formation of γ-l-glutamylpeptides in the l-glutamic acid fermentation. In the supposed mechanism, γ-l-GIu-l-GIu is formed mainly by the reversal of hydrolysis from l-glutamic acid being richly produced by the bacteria. The other four minor peptides are formed by the γ-glutamyltranspeptidatkm from γ-l-GIu-l-Glu to some α-l-amino acids and to γ-l-GIu-l-GIu itself in the broths. The enzyme was found to be widely distributed among bacteria, especially in some strains of Corynebacterium, Bacillus, Erwinea, Serratia, Pseu...