Biocatalytic Synthesis of gamma-glutamyl-L-leucine, a Kokumi-Imparting Dipeptide, by Bacillus licheniformis gamma-Glutamyltranspeptidase

Several -glutamyl compounds are known to have favorable features for a variety of biotechnological and pharmaceutical applications. However, so far only a limited number of -glutamyl compounds have been synthesized through -glutamyltranspeptidase (GGT). With the help of thin layer chromatography and computer-assisted image analysis techniques, we performed an enzymatic method involving Bacillus licheniformis GGT (BlGGT) for the synthesis of -glutamyl-L-leucine (-Glu-Leu). The optimum conditions for a biocatalytic synthesis of -Glu-Leu were determined to be 200mM glutamine, 200mM leucine, 50mM Tris-HCl buffer (pH 9.0), and BlGGT at a working concentration of 2.0U/mL. Upon a 5-h incubation of the reaction mixture at 50 degrees C, the product yield could reach approximately 52%. The preparative synthesis of -Glu-Leu by BlGGT was done under optimal conditions at millimol scale level. The reaction products were subjected to mass spectrometry/nuclear magnetic resonance analyses to ensure the successful synthesis of -Glu-Leu. Taken together, the present study demonstrates the high potentiality of BlGGT-catalyzed reaction in the synthesis of -glutamyl compounds.