A mutant Bacillus subtilis γ-glutamyltranspeptidase specialized in hydrolysis activity

gamma-Glutamyltranspeptidase (GGT) catalyzes the hydrolysis of gamma-glutamyl compounds and the transfer of their gamma-glutamyl moieties to amino acids and peptides. The transpeptidation activity of Bacillus subtilis GGT is about 10-fold higher than its hydrolysis activity. In B. subtilis GGT, substitution of Asp-445 with Ala abolished its transpeptidation activity. The specific activity for hydrolysis of D445A GGT was 40.2% of that of the wild-type GGT. The K-m value for (L)-glutamine was 15.3 mM. D445A GGT was salt tolerant like the wildtype GGT. These results indicate that D445A GGT will be highly useful as a 'glutaminase' in food industry. (C) 2003 Federation of European Microbiological Societies. Published by Elsevier Science B.V. All rights reserved.