Abstract:γ-Gminobutyric acid is an important biologically active factor, which is synthesized though the decarboxylation of L-glutamic acid by glutamate decarboxylase (GAD). The author firstly cloned and expressed the glutamate decarboxylase-encoding gene from Saccharomyces cerevisiae in E. coli. The specific activity of the recombinant ScGAD purified by affinity chromatography reached a maximum value of 66.55 U/mg. Further enzymatic property analysis results indicated that ScGAD exhibited an optimum reaction temperature of 60 ℃, an optimum reaction pH of 4.0, excellent stability in the range of 30~50 ℃ and pH 4.0~9.0, and the value of 14.28 mmol/L for kinetic constant Km indicating ScGAD of a good affinity to L-glutamic acid. Finally, through the investigation of the optimal conditions for GABA preparation by whole-cell catalysis using ScGAD, the highest generation efficiency of GABA was achieved at the conditions of 60 ℃ and pH 4.0. On this basis, 100 mmol/L of the substrate (sodium L-glutamate) could be converted to 35.9 g/(g·h) of GABA through whole-cell catalysis. This study provides a basis for efficient production of GABA.
