Quantum mechanical hydrogen tunneling in bacterial copper amine oxidase reaction
Quantum mechanical hydrogen tunneling in bacterial copper amine oxidase reaction
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DOI：
10.1016/j.bbrc.2006.01.150
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发表时间：
2006-04-07
影响因子：
3.1
通讯作者：
Tanizawa, K
中科院分区：
文献类型：
--
作者：
Murakawa, T;Okajima, T;Tanizawa, K
影响铜胺氧化酶催化效率的关键步骤是保守的Asp残基对底物α-质子的立体专一性提取。我们分析了这一步骤，通过使用细菌酶和立体声的稳定前动力学专门标记的氢。底物，2-苯乙胺和酪胺。在α质子提取过程中，2-苯乙胺观察到与温度相关的小的动力学同位素效应，而酪胺观察到与温度无关的大的动力学同位素效应，表明这一过程是由量子力学氢隧道机制驱动的，而不是经典的过渡态机制。此外，在缺乏关键天冬氨酸的突变酶的反应中，获得了接近过渡态值的Arrhenius型指前因子比。这些结果为酶增强的氢隧道效应提供了强有力的证据。反应中间产物的X射线晶体结构表明，底物远端的结合方式略有不同，这将通过主动或被动动力学来调制氢隧道过程。(C)2006 Elsevier Inc.保留所有权利。
A key step decisively affecting the catalytic efficiency of copper amine oxidase is stereospecific abstraction of substrate a-proton by a conserved Asp residue. We analyzed this step by pre-steady-state kinetics using a bacterial enzyme and stereo specifically deuterium-labeled. substrates, 2-phenylethylamine and tyramine. A small and temperature-dependent kinetic isotope effect (KIE) was observed with 2-phenylethylamine, whereas a large and temperature-independent KIE was observed with tyramine in the a-proton abstraction step, showing that this step is driven by quantum mechanical hydrogen tunneling rather than the classical transition-state mechanism. Furthermore, an Arrhenius-type preexponential factor ratio approaching a transition-state value was obtained in the reaction of a mutant enzyme lacking the critical Asp. These results provide strong evidence for enzyme-enhanced hydrogen tunneling. X-ray crystallographic structures of the reaction intermediates revealed a small difference in the binding mode of distal parts of substrates, which would modulate hydrogen tunneling proceeding through either active or passive dynamics. (c) 2006 Elsevier Inc. All rights reserved.