【摘要】 从最近分离到的有机磷农药降解菌Pseudomonassp .WBC 3中获得了甲基对硫磷水解酶 (Methylparathionhydrolase,MPH ,EC 3 1 8 3)。该酶在 48h的培养物中分布比例分别为 :上清液 2 1 % ,胞内 86 2 %和胞间质 1 1 7% ,说明MPH为胞内酶。经过CM sepharoseFastFlow阳离子交换层析 ,获得电泳纯的酶。SDS PAGE和凝胶过滤层析表明 ,该酶为单体蛋白 ,分子量约为 34kD。动力学分析显示该酶为非特异性有机磷降解酶 ,但最适底物为甲基对硫磷。在pH9～ 1 2范围 ,酶表现较高活力水平 ,最高活力的反应温度为 40℃。根据各类金属离子和鳌合剂对酶活的影响 ,推测MPH为金属酶。更多还原

【Abstract】 A methyl parathion degradation enzyme, or methyl parathion hydrolase (MPH, EC 3.1.8.1), locating in the soluble intracellular fraction of Pseudomonas sp. WBC-3, was purified 49.1-fold to homogeneity by one-step ion exchange chromatography. The physical and chemical properties of the purified MPH were studied. The purified MPH displayed relatively broad optimal temperature around 40℃. The activity of MPH was affected by pH and the optimal pH was 11.0. Cd 2+ and Fe 2+ could enhance the catalytic efficiency of MPH while Hg 2+ , Zn 2+ , Al 3+ and Bi 3+ showed inhibition effect. With methyl parathion as the optimal substrate, the K _m was 0.0807mmol/L and the k _ cat was 2.1×10 6 min -1 . In addition, the comparison of native and subunit molecular weights of MPH suggested that this enzyme was a monomer of approximate 34kD.更多还原