Abstract: Gama-aminobutyric acid ( GABA) is synthesized from L- glutamate using L- glutamate decarboxylase ( GAD) .However, the optimum pH of wild-type L-glutamate decarboxylase is rather low, which limited its industrial application.In this report, site- directed mutagenesis and over- expression of gadB gene in E. coli encoding L-glutamate decarboxylase was performed in E. coli host cells, and enzymatic characterization of recombinant enzymes were investigated in term of their temperature optimum, pH optimum, thermostability and pH stability.GadBΔHT showed broader pH adaptability, at pH 3.4 ~ 6.2, its relative catalytic activity maintain above 50%comparing to wild- type enzyme. Thus, the engineered GadΔHT overcomes the drawback of native enzyme by displaying broader pH tolerance, that could better meet the requirement of industrial bio-production of GABA.