Hydrogen Tunneling in Enzyme Reactions

酶反应中的氢隧道

• 批准号: 9221072
• 负责人: Judith Klinman
• 金额: $ 24万
• 依托单位: University of California-Berkeley
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1993
• 资助国家: 美国
• 起止时间: 1993-01-15 至 1995-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9221072&HistoricalAwards=false
• 关键词: Hydrogen; Tunneling; Enzyme; Reactions

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.

文献中存在大量例子来证明电子隧道效应在酶促过程中的重要性。 尽管氕比电子大得多，但其德布罗吉波长与简单氢转移反应中反应坐标的预期尺寸相似。 这一特性使人们认识到氕的行为介于经典力学行为和量子力学行为之间。 该实验室发表的研究表明，量子效应对室温下几种酶催化的氢转移反应有显着贡献。 正在进行的实验表明，这种现象将是酶催化反应的普遍现象。 明确演示隧道掘进的一个主要困难是缺乏合适的实验探针。为此开发了一系列协议：其中包括 H/T 和 D/T 同位素效应及其温度依赖性的比较研究。 下一个资助期间的研究将包括以下几个方面：（1）将检查一些新的酶催化H转移反应的隧道效应，以便建立这种现象的数据库。 特别是，PI计划重点关注含黄素的酶、单胺氧化酶和葡萄糖氧化酶：（2）将通过使用定点诱变来研究对特定蛋白质底物相互作用的隧道效应的影响； （3）将继续进行计算工作，目标是重现实验数据并为酶反应中的隧道机制提供合适的模型。 %%% 尽管蛋白质中的电子隧道效应已被广泛研究，但核（氢）隧道效应却很少受到关注。 克林曼博士的出色工作表明，核隧道效应对生物学相关条件下的某些酶促反应速率有显着贡献。 该项目建立并扩展了这些突破性的观察结果。