Alpha-secondary isotope effects as probes of "tunneling-ready" configurations in enzymatic H-tunneling: insight from environmentally coupled tunneling models.
Alpha-secondary isotope effects as probes of "tunneling-ready" configurations in enzymatic H-tunneling: insight from environmentally coupled tunneling models.
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α-二级同位素效应作为酶 H 隧道中“隧道就绪”构型的探针：来自环境耦合隧道模型的见解。
DOI：
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发表时间：
2006
影响因子：
15
通讯作者：
N. Scrutton
中科院分区：
文献类型：
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作者：
C. Pudney;Sam Hay;M. Sutcliffe;N. Scrutton
使用α-二级动力学同位素效应（2度KIEs）结合初级（1度）KIEs，我们已经研究了环境耦合的氢隧道在两个同源的黄素酶，吗啡酮还原酶（MR）和季戊四醇四硝酸还原酶（PETNR）的还原半反应的机制。我们发现这两种酶的KIEs（1.17-1.18）升高了2度，与氢隧穿一致。这些2度KIE，不像1度KIE，是独立的促进运动的非平衡预组织的辅因子和活性位点残基，需要使反应物进入一个“隧道准备”的配置。这些2度KIE是相同的，这表明两种酶中的“隧穿就绪”构型的几何形状是不可区分的，尽管MR而不是PETNR具有明显的温度依赖性1度KIE。这项工作强调了1度和2度KIE结合研究的好处，报告在当代环境耦合框架H-隧道的背景下，预组织和局部几何形状。
Using alpha-secondary kinetic isotope effects (2 degrees KIEs) in conjunction with primary (1 degrees ) KIEs, we have investigated the mechanism of environmentally coupled hydrogen tunneling in the reductive half-reactions of two homologous flavoenzymes, morphinone reductase (MR) and pentaerythritol tetranitrate reductase (PETNR). We find exalted 2 degrees KIEs (1.17-1.18) for both enzymes, consistent with hydrogen tunneling. These 2 degrees KIEs, unlike 1 degrees KIEs, are independent of promoting motions-a nonequilibrium pre-organization of cofactor and active site residues that is required to bring the reactants into a "tunneling-ready" configuration. That these 2 degrees KIEs are identical suggests the geometries of the "tunneling-ready" configurations in both enzymes are indistinguishable, despite the fact that MR, but not PETNR, has a clearly temperature-dependent 1 degrees KIE. The work emphasizes the benefit of combining studies of 1 degrees and 2 degrees KIEs to report on pre-organization and local geometries within the context of contemporary environmentally coupled frameworks for H-tunneling.