二氢叶酸还原酶催化过程中环境耦合氢隧穿的证据。

Evidence for environmentally coupled hydrogen tunneling during dihydrofolate reductase catalysis.

作者信息

Maglia Giovanni, Allemann Rudolf K

机构信息

School of Chemistry, University of Birmingham, Edgbaston, Birmingham, B15 2TT, United Kingdom.

出版信息

J Am Chem Soc. 2003 Nov 5;125(44):13372-3. doi: 10.1021/ja035692g.

DOI:10.1021/ja035692g

PMID:14583029

Abstract

Hydride transfer during catalysis by dihydrofolate reductase from Thermotoga maritima has been studied by stopped flow spectroscopy. The reduction of dihydrofolate by NADPH showed a biphasic temperature dependence of the deuterium kinetic isotope effect. At temperatures above 25 degrees C the KIE was temperature independent, while the reaction rates were strongly temperature dependent. Below 25 degrees C the KIE becomes dependent on temperature, and the ratio of the preexponential factors is inverse, suggesting a greater role for active dynamics that modulate the tunneling distance.

摘要

利用停流光谱法研究了嗜热栖热菌二氢叶酸还原酶催化过程中的氢化物转移。NADPH对二氢叶酸的还原显示出氘动力学同位素效应的双相温度依赖性。在25摄氏度以上的温度下，动力学同位素效应与温度无关，而反应速率强烈依赖于温度。在25摄氏度以下，动力学同位素效应变得依赖于温度，且指前因子的比值呈反比，这表明活性动力学在调节隧穿距离方面发挥了更大的作用。