The hydrogen transfer reaction catalysed by soybean lipoxygenase (SLO) has been the focus of intense study following observations of a high kinetic isotope effect (KIE). Today high KIEs are generally thought to indicate departure from classical rate theory and are seen as a strong signature of tunnelling of the transferring particle, hydrogen or one of its isotopes, through the reaction energy barrier. In this paper, we build a qualitative quantum rate model with few free parameters that describes the dynamics of the transferring particle when it is exposed to energetic potentials exerted by the donor and the acceptor. The enzyme’s impact on the dynamics is modelled by an additional energetic term, an oscillatory contribution known as “gating.” By varying two key parameters, the gating frequency and the mean donor-acceptor separation, the model is able to reproduce well the KIE data for SLO wild-type and a variety of SLO mutants over the experimentally accessible temperature range. While SLO-specific constants have been considered here, it is possible to adapt these for other enzymes.

中文翻译：

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大豆脂氧合酶中氢转移的定性量子速率模型

在观察到高动力学同位素效应（KIE）之后，大豆脂氧合酶（SLO）催化的氢转移反应一直是研究的重点。如今，人们普遍认为，高KIE表示偏离经典速率理论，并被视为转移粒子，氢或其同位素之一通过反应能垒隧穿的有力标志。在本文中，我们建立了一个具有很少自由参数的定性量子速率模型，该模型描述了转移粒子暴露于供体和受体所施加的高能电势时的动力学。酶对动力学的影响可以通过一个附加的能量项来建模，该能量项被称为“门控”（gating）。通过更改两个关键参数，即门控频率和平均供体-受体间隔，该模型能够很好地重现SLO野生型和各种SLO突变体在实验上可达到的温度范围内的KIE数据。尽管此处考虑了SLO特定的常数，但可以将其修改为适用于其他酶。