肉碱脱水酶突变株的获得及其休止细胞反应条件的优化

Obtaining a mutant with carnitine-dehydratase and the optimizing of reactive conditions of rest cells

对一株产肉碱脱水酶的菌株用溴化乙锭进行诱变 ,并经肉碱选择性培养基进行筛选 ,获得了一株高活性酶活的菌株 ,并进行了休止细胞转化巴豆甜菜碱为L 肉碱的反应条件的研究。实验确定休止细胞的最适反应温度为 30℃～ 32℃ ,pH8.1、0 .0 1mol L磷酸缓冲液 ,时间 8.5～ 10h。最适底物浓度为 6 0mg ml,最适休止细胞浓度为 6 0mg ml(湿重 ) ,产率 4 0 % (摩尔比 )。建立了休止细胞酶反应的表观米氏方程 ,其中Vm =0 .0 0 12 2 5mol (min·15mg菌体 ) ,Km =0 .0 4 0 114mol L。

A mutant with high enzyme(carnitine dehydratase) activity was obtained from E.coli which was mutagenized by EB and selected from the carnitine-selective culture medium. The study on the reactive condition of rest cells of mutant strain , which has carnitine-dehydratase, was proceed. Throughexperiments the optium conditions of reaction were found: the temperature between 30℃ and 32℃,pH 8.1-0.01 mol/L phosphate buffer,time between 8.5 and 10 hours, crotonobetaine 60 mg/ml,rest cells 60 mg/ml(wet weight),products about 40%(mole rate).At the same time the Monod model of the rest cell reaction was set up. The V m was 0.001 225 mol/(min·15 mg cell),K m was 0.040 144 mol/L-