Abstract:

Glutathione peroxidase (GPx) is an antioxidant enzyme in vivo. For expanding the application of GPx in vitro, imitating GPx functions has aroused great interest. The pH-sensitive GPx artificial enzymes that utilize natural pH differences in living organisms to achieve responses have a wide range of potential applications. However, up to now, the activities of pH sensitive GPx mimics are relatively low. Thus, organic tellurium compound I, which contains high activity catalytic center of glutathione peroxidase (GPx) and two primary amine groups, was designed and synthesized in this research. The enzymatic reaction kinetics measurement results demonstrated that the second order reaction rate constant of compound I was at the level of as high as 10¹ L·mol^-1·min^-1. Compound I formed molecular machine with CB[6] at pH=6. In this case, only (0.04±0.02) μmol·min^-1·μmol^-1 GPx activity was shown as the active site was encapsulated into CB[6] and thereby cannot bind substrate. Molecular machine was partly dissociation when only one of the two primary amine groups was protonated at pH=7. In this case, (0.35±0.06)μmol·min^-1·μmol^-1 GPx activity was shown as the active site gradually exposed to solution. The high activity pH sensitive artificial glutathione peroxidase was constructed through the formation and partly dissociation of molecular machine formed by compound I and CB[6] by changing pH between 6 and 7.

Key words: enzyme, glutathione peroxidase, catalysis, biocatalysis, molecular machine, pH sensitive

摘要：

谷胱甘肽过氧化物酶（GPx）是体内一种重要的抗氧化酶，对GPx的人工模拟能够拓展其体外应用，利用生命体内天然pH差异实现响应的pH敏感性GPx人工酶更是有着广泛的潜在应用。然而目前制备的pH敏感性GPx人工酶普遍存在活性较低的缺点，本文设计合成了同时含有高活性GPx催化中心和两个伯胺基团的乙胺单碲醚分子，酶促反应动力学的分析结果表明其二级反应速率常数高达10¹ L·mol^-1·min^-1数量级。pH=6时，乙胺单碲醚分子能够与葫芦[6]脲分子（CB[6]）组装形成分子机器，此时活性中心被包埋于CB[6]的疏水空腔之中，仅能展现出（0.04±0.02）μmol·min^-1·μmol^-1的活性；pH=7时，分子机器部分分解，能够展现出高达（0.35±0.06）μmol·min^-1·μmol^-1的活性。因此，通过调控体系pH在6和7之间变化，借助分子机器的组装及部分分解调控人工酶活性的关闭与开启，从而构建了高活性的pH敏感性GPx人工酶。

关键词: 酶, 谷胱甘肽过氧化物酶, 催化, 生物催化, 分子机器, pH敏感性