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首页> 外文期刊>Israel journal of chemistry >Enzymatic H Transfers: Quantum Tunneling and Coupled Motion from Kinetic Isotope Effect Studies
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Enzymatic H Transfers: Quantum Tunneling and Coupled Motion from Kinetic Isotope Effect Studies

机译：酶促转移：动力学同位素效应研究的量子隧穿和耦合运动

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摘要

Many hydrogen transfer processes exhibit nonclassical behavior due to inherent quantum mechanical properties of the hydrogen. Investigation of various enzymes under physiological conditions indicates that hydrogen transfer processes often show significant quantum mechanical behavior. Traditionally, this phenomenon was treated in terms of a tunneling correction to classical or semiclas-sical models. However, more recently, it has been observed that increasing numbers of enzymes yield data that cannot be rationalized by tunneling correction models. Observations such as large kinetic isotope effects (KIEs ) with unusual temperature dependence, isotope effects on Arrhenius preexponential factors with values different from semiclassical predicted ranges, and small temperature-independent KIEs for processes with significant energy of activation, could only be explained with full tunneling models for H transfer. Full tunneling models presume that the solvent or protein fluctuations generate a reactive configuration along the heavy-atom coordinate, from which the hydrogen is transferred through quantum mechanical tunneling. These models are sometimes denoted as environmentally coupled tunneling (ECT) or Marcus-like models, and they link protein dynamics to the catalyzed H transfer. Several enzymatic systems (dihydrofolate reductase, thymidylate synthase, and soybean lipoxygenase) are presented as case studies of proton, hydrogen, and hydride transfer.
机译：由于氢的固有量子机械性能，许多氢转移过程都表现出非典型行为。在生理条件下对各种酶的研究表明，氢转移过程通常显示出明显的量子机械行为。传统上，这种现象是根据对经典或半法学模型的隧道校正来处理的。但是，最近，已经观察到，越来越多的酶产生的数据无法通过隧道校正模型合理化。诸如具有异常温度依赖性的大动力学同位素效应（KIE），同位素对ARRHENIUS PREEXPOREADENTIANTAINT的效应的观测值与半经典预测范围不同，并且与温度无关的KIE的值不同，并且具有显着激活能量的过程，只能通过完整的隧道来解释。 H传输的模型。完整的隧道模型假定溶剂或蛋白质波动会沿重原子坐标产生反应性构型，从而通过量子机械隧道转移氢。这些模型有时表示为环境耦合的隧道（ECT）或类似MARCUS模型，它们将蛋白质动力学与催化的H转移联系起来。将几种酶促系统（二氢叶酸还原酶，胸苷酸合酶和大豆脂氧酶）表示为质子，氢和氢化物转移的案例研究。

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