多酚氧化酶催化儿茶酚的动力学及机理研究

STUDY ON THE KINETICS AND REACTION MECHANISM OF POLYPHENOLOXIDASE CATALYSISING CATECHOL

本研究采用冷丙酮二次提取法从马铃薯中提取出多酚氧化酶,用微量呼吸仪和氧电极测定酶的最适 pH 为7,最适反应温度为25℃。通过对多酚氧化酶活性中心的测定和探讨,认为活性中心起催化作用的是二价铜(Ⅱ),两个铜离子(Ⅱ)之间的距离与儿茶酚两个羟基间的距离一致。双底物动力学结果证明,反应是以氧首先进攻酶的活性中心的强制有序三元复合物的机理。本文还用最小二乘方法回归出了动力学常数,求出了反应的活化能等重要的动力学参数。

Potato Polyphenoloxidase(PPO)is extracted two times by coldacetone.The writers use warburg manometer and oxygen electrodetechnique to study PPO,and the experiments exhibit that pH Opti-mum is 7 and temperature optimum 25℃.Cu(Ⅱ)plays an importantpart in PPO active center.The distance of the two Cu(Ⅱ)is thesame with that of two O-hydroxyl of Catechol.Further studying totwo substrates kinetics,the experiment indicates that Oxygen bent enzyme first and the reaction is ompulsoryordered tennary complex.Least square method is used to obtain kinetics parameter in whichthe active energy is a very important One.