y-aminobutyric acid (GABA), a free non-protein amino acid, acts as a major inhibitory neurotransmitter in the central nervous system. GABA has several physiological functions such as neurotransmission, induction of hypotensive effects, diuretic effects, treatment of epilepsy and tranquilizer effects, regulation of hormone secretion, activation hepatorenal, etc. Preparation and application of GABA were received by people's concern and attention. The glutamate decarboxylase (GAD, EC 4.1.1.15) catalyze L-gluta...