Enzymatic Synthesis of γ-Glutamylvalylglycine Using Bacterial γ-Glutamyltranspeptidase

gamma-Glutamylvalylglycine is known as a potent "kokumi" substance that increases the thickness, continuity, and mouthfulness of the taste of food. In this study, gamma-glutamylvalylglycine was enzymatically synthesized from glutamine and valylglycine through the transpeptidation reaction of bacterial gamma-glutamyltranspeptidase. The reaction conditions decided for the production of gamma-glutamylvalylglycine are 20 mM glutamine, 100 mM valylglycine, 30 mU/mL gamma-glutamyltranspeptidase, and 0.856 M (5%) NaCl at pH 8 and 37 degrees C, and 18.6 mM gamma-glutamylvalylglycine was synthesized. Metal cations, Na+ and Mg2+, improved the transpeptidation reaction of gamma-glutamyltranspeptidase, and the production of gamma-glutamylvalylglycine increased. Moreover, by feeding a suitable amount of glutamine every 5 h, the maximum production of gamma-glutamylvalylglycine increased 1.7 times after 20 h of incubation.