A mutant Bacillus subtilis gamma-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 wild-type GGT. These results indicate that D445A GGT will be highly useful as a 'glutaminase' in food industry.