Quantum wavepacket ab initio dynamical studies of hydrogen transfer catalysis in

描述（由申请人提供）：Srinivasan S酶中氢转移催化的量子波包从头算动力学研究。Iyengar印第安纳州大学摘要这一提议涉及酶中氢转移过程的基本分子水平描述。考虑两种酶：（a）大豆脂氧合酶-1（SLO-1）是催化脂肪酸氧化的非血红素金属酶。在哺乳动物中，脂氧合酶催化白三烯和脂氧素的产生，并在炎症反应中起重要作用。抑制这种酶可抑制肿瘤发生。因此，脂氧合酶被认为是一种很有前途的癌症化学预防剂。(b)嗜热醇脱氢酶（ADH），促进醇转化为醛，并防止有毒醇在哺乳动物肝脏中的积累。这些酶对计算机模拟方案提出了积极的挑战，因为它们表现出意想不到的氢/氘/氚动力学同位素效应。这些同位素效应背后的根本原因被认为是基于量子力学隧穿。这里提出的计算处理采用了一种新的时间依赖性，第一性原理方法，在PI。的集团。它允许通过量子波包动力学和从头算分子动力学之间的协同作用，通过电子和原子核的同时动力学的大系统的有效量子动力学。在SLO-1中，我们将研究在最近的实验中看到的异常主要动力学同位素效应，通过隧道氢核的量子力学动力学与活性位点和周围氨基酸的经典动力学的同时，并使用AIMD与QM/MM近似同时确定电子结构。这里进行的详细描述，通过计算诱变研究，将阐明从氨基酸基团和金属中心的贡献。对于ADH，我们将试图描述在最近的实验表明初级（转移）氢原子和次级核之间的耦合迷人的次级动力学同位素效应。量子动力学方法将被推广到处理多粒子（初级氢和次级粒子）在并行的同时经典动力学的活性位点，并同时确定电子结构。这一目标将通过一系列拟议的方法进步来实现。这些研究将在前所未有的量子动力学水平上确定酶活性位点中不同核之间的耦合。还将探讨氨基酸取代和金属中心置换的影响。次级同位素效应是反应坐标的直接探测器。因此，我们的方法将对生物和合成酶中的所有氢转移反应产生影响。 公共卫生相关性：该建议涉及新的计算方法的发展，将被用来进行一个基本的分子水平上的氢转移过程中的两种生物酶：大豆脂肪氧合酶-1（SLO-1）和高温嗜热醇脱氢酶（ADH）的研究。计算方法是基于量子力学，并特别设计来了解这些酶的功能上的氢隧道的影响。

DESCRIPTION (provided by applicant): Quantum wavepacket ab initio dynamical studies of hydrogen transfer catalysis in enzymes Srinivasan S. Iyengar Indiana University Abstract This proposal deals with the fundamental molecular level description of hydrogen transfer processes in enzymes. Two enzymes are considered: (a) Soybean Lipoxygenase-1 (SLO-1) is a non-heme metalloenzyme that catalyzes oxidation of fatty acids. In mammals, lipoxygenase catalyzes the production of leukotrienes and lipoxins and plays an important role in inflammatory response. Inhibition of this enzyme inhibits tumor-genesis. Thus lipoxygenase has been proposed as a promising cancer chemopreventive agent. (b) Thermophilic alcohol dehydrogenase (ADH), facilitates conversion of alcohols to aldehydes and prevents accumulation of toxic alcohols in mammalian livers. These enzymes present an active challenge to computer simulation protocols since they exhibit unexpected hydrogen/deuterium/tritium kinetic isotope effects. The fundamental reason behind these isotope effects is believed to be based on quantum mechanical tunneling. The computational treatment proposed here utilizes a new time-dependent, first principles method, developed in the P.I.'s group. It allows efficient quantum dynamics of large systems through simultaneous dynamics of electrons and nuclei via a synergy between quantum wavepacket dynamics and ab initio molecular dynamics. In SLO-1, we will study the abnormal primary kinetic isotope effect seen in recent experiments, through simultaneous quantum mechanical dynamics of the tunneling hydrogen nucleus with classical dynamics of active site and surrounding amino acids, and concurrent determination of electronic structure using AIMD with QM/MM approximations. The detailed description undertaken here, through computational mutagenesis studies, will elucidate contributions from amino acid groups and the metal centers. For ADH, we will attempt to describe the fascinating secondary kinetic isotope effects in recent experiments which indicate coupling between primary (transferring) hydrogen atoms and secondary nuclei. The quantum dynamics approach will be generalized to treat multiple particles (primary hydrogens and secondary particles) in parallel with simultaneous classical dynamics of active site, and concurrent determination of electronic structure. This goal will be achieved through a series of proposed methodological advances. The studies will determine, at an unprecedented quantum dynamical level, the coupling between different nuclei in the enzyme active site. The effect of amino acid substitutions and metal center replacements will also be probed. Secondary isotope effects are a direct probe of the reaction coordinate. Hence, our approach will have impact on all hydrogen transfer reactions in biological and synthetic enzymes. PUBLIC HEALTH RELEVANCE: This proposal pertains to the development of new computational methods that will be utilized to conduct a fundamental molecular level study of hydrogen transfer processes in two biological enzymes: Soybean Lipoxygenase-1 (SLO-1) and high temperature thermophilic alcohol dehydrogenase (ADH). The computational methods are based on quantum mechanics and are especially designed to understand the implications of hydrogen tunneling on the function of these enzymes.