Improving the enzymatic activity of l-amino acid α-ligase for imidazole dipeptide production by site-directed mutagenesis.

Imidazole dipeptides, histidine-containing dipeptides, including carnosine (ß-alanyl-l-histidine), anserine (ß-alanyl-3-methyl-l-histidine), and balenine (ß-alanyl-1-methyl-l-histidine) in animal muscles have physiological functions, such as significant antioxidant and antifatigue effects. They are obtained by extraction from natural raw materials, including chicken and fish meat. However, using natural raw materials entails stable supply and mass production limitations. l-amino acid α-ligase (Lal) catalyzes the formation of various dipeptides from unprotected l-amino acids by conjugating with adenosine 5'-triphosphate (ATP) hydrolysis reaction. In this study, site-directed mutagenesis of Lal was applied to establish an efficient method for producing imidazole dipeptides by the enzymatic process. We significantly improved the conversion rate from substrate amino acids compared with wild-type Lal.