【作者】 闫龙飞； 张浩； 杨玲；

【Author】 Longfei Yan;Hao Zhang;Ling Yang;School of Chemistry and Chemical Engineering,Harbin Institute of Technology;College of Life Science and Engineering,Northwest University for Nationalities;

【机构】 哈尔滨工业大学化工与化学学院； 西北民族大学生命与科学学院；

【摘要】 含钙β-螺旋蛋白质哺乳类动物血清对氧磷酶1(PON1)和磷酸三酯酶二异丙基氟磷酸酶(DFPase)活性位点的结构相似,存在着进化相关性。二者均能催化有机磷化合物和各种神经药剂的水解。在本研究中,我们采用杂化密度泛函理论方法B3LYP结合从晶体结构中选取的活性中心模型对PON1和DFPase以水分子为亲核试剂的反应机理进行了研究。基于PON1和DFPase活性位点的不同,我们分别设计了野生型和突变型(在PON1中一个水分子替代Asn270)PON1和DFPase的四种活性中心模型。计算结果显示,通过降低反应能垒并提高产物的稳定性,突变提高了DFPase对底物DFP的催化活性;而突变会降低PON1对底物的催化效率。这表明从一类酶优于催化底物对氧磷进化到另一类酶优先催化二异丙基氟磷可由Asn270的突变来调节。这种进化关系的研究结果可能引导未来实验室关于酶的设计。更多还原

【Abstract】 The calcium-dependent β-propeller proteins mammalian serum paraoxonase 1(PON1) and phosphotriesterase diisopropyl fluorophosphatase(DFPase), sharing similar active sites, are evolutionally related, and catalyze the hydrolysis of organophosphorus compounds and various nerve agents. In the present work, the reaction mechanisms of PON1 and DFPase via the nucleophilic attacking of a water molecule were investigated using the hybrid density functional theory(DFT) method B3 LYP. Based on the difference between the active sites of PON1 and DFPase, the wild type and mutant(a water molecule replacing Asn270 in PON1) models were designed. The calculated results indicated that this mutation improves the enzyme activity for substrate DFP with lower energy barrier and more stable product, while reversed for paraoxon. It suggests an evolutional trend from the enzyme preferring paraoxon to those preferring DFP mediated by the mutation of Asn 270 and may guide enzyme design in the laboratory.更多还原