假单胞菌WBC—3甲基对硫磷水解酶性质的初步研究

从最近分离到的有机磷农药降解菌Pseudomonas sp．WBC—3中获得了甲基对硫磷水解酶（Methyl parathion hydrolase，MPH，EC3．1．8．3)。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11．7％，说明MPH为胞内酶。经过CM—sepharose Fast Flow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pH9～12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。

Study on the Properties of Methyl Parathion Hydrolase from Pseudomonas sp. WBC-3

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 degrees. The activity of MPH was affected by pH and the optimal pH was 11.0. Cd2+ and Fe2+ could enhance the catalytic efficiency of MPH while Hg2+, Zn2+, Al3+ and Bi3+ showed inhibition effect. With methyl parathion as the optimal substrate, the Km was 0.0807mmol/L and the kcat was 2.1 x 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.