γ-Glutamylpeptide Formative Activity of Corynebacterium glutamicum by the Reverse Reaction of the γ-Glutamylpeptide Hydrolytic Enzyme

Abstract

To clarify the mechanism of the γ-L-glutamylpeptide formation in the L-glutamic acid fermentation with Corynebacterium glutamicum, γ-glutamylpeptide synthetic activity of the intact cells and the cell extracts of the bacteria was studied. γ-L-Glu-L-Glu and other various γ-glutamylpeptides were formed by these crude preparations under high substrate amino acid concentrations without direct or indirect biological energy supplying systems. It was re-vealed that these enzyme preparations possessed strong hydrolytic activity to γ-glutamyl-peptides, and that notable amounts of these peptides could be formed by the reverse reaction of the hydrolysis. These reactions were found to be catalyzed by an enzyme. To give the evidence, the equilibrium constants of the hydrolysis of γ-L-glutamylpeptides, the substrate specificity and the distribution of the enzyme among various strains of the bacteria were studied. The partial purification of the enzyme gave sufficient proof to the idea. The mecha-nism was thought to contribute to the γ-L-GIu-L-Glu formation in the fermentation.