Hydrogen Tunneling in Enzyme Reactions

文献中有许多例子记录了 电子隧穿在酶过程中的重要性。 虽然 比电子大得多的具有德布罗意波 与反应的预期尺寸相似的长度 在简单的H转移反应中配位。 该物业已导致 我们认识到， 经典和量子力学行为。 发表的研究来自 这个实验室已经证明量子效应 对几种酶催化的H转移反应有显著影响， 室温 正在进行的实验表明， 将是酶催化反应的一个通用模型。 一个主要 在明确证明隧道的困难一直是 缺乏合适的实验探针。一系列协议 已经朝着这个目标发展：这些包括比较 H/T和D/T同位素效应及其温度研究 依赖 下一个供资期间的调查将 包括以下几个方面：（1）一些新的酶催化 H转移反应将检查隧道效应，以便 为这一现象建立数据库。 特别是，PI 计划集中在黄素含有酶，单胺氧化酶 和葡萄糖氧化酶：（2）研究了葡萄糖氧化酶对隧道效应的影响。 特异性蛋白质底物相互作用将通过 使用位点特异性诱变;和（3）计算工作将 继续进行，目的是再现实验数据， 为酶的隧穿机制提供了合适的模型 反应. %%% 尽管蛋白质中的电子隧穿已经被广泛地研究， 研究，很少注意到核（氢） 隧道 克林曼博士出色的工作表明， 隧道效应对某些酶促反应有重要作用 在生物学相关条件下。 该项目建立 并扩展了这些突破性的观察。

Numerous examples exist in the literature documenting the importance of electron tunneling in enzymatic processes. Although much larger than the electron, protium possesses a de Brogile wave length which is similar to the expected dimension of the reaction coordinate in simple H transfer reactions. This property has led to the recognition that the behavior of protium is poised between classical and quantum mechanical behavior. Published studies from this laboratory have demonstrated that quantum effects contribute significantly to several enzyme catalyzed H transfer reactions at room temperature. Ongoing experiments suggest that this phenomenon will be a general one for enzyme catalyzed reactions. A major difficulty in the unambiguous demonstration of tunneling has been the absence of suitable experimental probes. A series of protocols have been developed toward this end: these include the comparative study of H/T and D/T isotope effects and their temperature dependences. Investigations during the next funding period will include the following areas: (1) A number of new enzyme catalyzed H transfer reactions will be examined for tunneling, in order to establish a data base for this phenomenon. In particular, the PI plans to focus on the flavin containing enzymes, monoamine oxidase and glucose oxidase: (2) Studies of the influence on tunneling of specific protein substrate interactions will be pursued through the use of site-specific mutagenesis; and (3) Computational work will be continued, with the goal of reproducing experimental data and providing suitable models for the mechanism of tunneling in enzyme reactions. %%% Although electron tunneling in proteins has been extensively studied, little attention has been paid to nuclear (hydrogen) tunneling. Dr. Klinman's elegant work has shown that nuclear tunneling contributes significantly to certain enzymatic reaction rates under biologically relevant conditions. This project builds and expands upon these groundbreaking observations.