米糠谷氨酸脱羧酶的分离纯化及酶学性质研究

利用（NH4）2SO4分级沉淀、DEAE-Sephrose FF离子交换色谱技术分离纯化米糠谷氨酸脱羧酶（GAD）。米糠GAD纯化倍数为8·8,比活达到了30·1U/mg,酶活回收率为45·5%。同时对米糠GAD酶学性质进行了研究,结果表明,最适温度为40℃,耐热性较差;最适pH5·5,在pH5·5～9都可以保持较高酶活。米糠GAD对底物和辅酶PLP的Km分别为28·45、1·13μmol/L。KI、Ag+、SDS、乙酸对米糠GAD的活力有较大的抑制作用,而Ca2+对米糠GAD的活性有较强的激活作用。 

Purification and characterization of glutamate decarboxylase from rice bran

Glutamate decarboxylase (GAD) was purified by using ( NH_4 )_2 SO_4 fractionation and DEAE- Sephrose FF ion exchange chromatography.GAD was purified 8.8-folds.The specific activity was 30.1 U/mg, and the enzymatic activity recovery was 45.5%.The optimum temperature of GAD was 40℃, and it was inactive at 70℃.The optimum pH was 5.5 ,and it was stable at pH5.5～9.0.K_m values for GAD and PLP were determined at 28.45 and 1.13μmol/L, respectively.Chemicals reagent s such as Kl ,Ag~+ , SDS and acetic acid decreased the enzyme activity, but Ca~(2+) increased the GAD activity greatly.