Expression and characterization of glutamate decarboxylase from Lactobacillus brevis HYE1 isolated from kimchi

A putative gene ( gadlbhye1 ) encoding glutamate decarboxylase (GAD) was cloned from Lactobacillus brevis HYE1 isolated from kimchi , a traditional Korean fermented vegetable. The amino acid sequences of GAD Lb HYE1 showed 48% homology with the GadA family and 99% identity with the GadB family from L. brevis . The cloned GAD Lb HYE1 was functionally expressed in Escherichia coli using inducible expression vectors. The expressed recombinant GAD Lb HYE1 was successfully purified by Ni–NTA affinity chromatography, and had a molecular mass of 54 kDa with optimal hydrolysis activity at 55 °C and pH 4.0. Its thermal stability was determined to be higher than that of other GADs from L. brevis , based on its melting temperature (75.18 °C). Kinetic parameters including K m and V max values for GAD Lb HYE1 were 4.99 mmol/L and 0.224 mmol/L/min, respectively. In addition, the production of gamma-aminobutyric acid in E. coli BL21 harboring gadlbhye1 /pET28a was increased by adding pyridoxine as a cheaper coenzyme.