Loss of Hyperconjugative Effects Drives Hydride Transfer during Dihydrofolate Reductase Catalysis.
Loss of Hyperconjugative Effects Drives Hydride Transfer during Dihydrofolate Reductase Catalysis.
复制标题
超共轭效应的丧失会在二氢叶酸还原酶催化过程中驱动氢化物转移。
DOI：
10.1021/acscatal.9b02839
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发表时间：
2019
期刊：
影响因子：
12.9
通讯作者：
Angelastro A
中科院分区：
文献类型：
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作者：
Angelastro A
氢化物转移在自然界广泛存在，在应用研究中具有重要作用。然而，这种转变如何在生物体中发生的机制仍然是一个激烈争论的问题。在这里，我们检测了二氢叶酸还原酶（DHFR），一种催化NADPH的C4 '氢化成7,8-二氢叶酸（H2F）的C6的酶。尽管对该反应的机理进行了许多研究，但H2F π键的极化在驱动氢化物转移中的作用仍不清楚。在反应中心用β氘立体定向标记H2F，并测量了β-氘的动力学同位素效应。我们的实验结果与QM/MM模拟的分析结果相结合，表明氢化物转移是由H2F的C6极化引发的。在化学转变过程中，σ c - β - h键有助于阳离子特征的形成，超共轭作用影响过渡态的形成。我们的发现为dhfr催化反应的氢化物转移机制提供了关键的见解，该反应是抗增殖药物的靶点，也是机制酶学的典范模型。
Hydride transfer is widespread in nature and has an essential role in applied research. However, the mechanisms of how this transformation occurs in living organisms remain a matter of vigorous debate. Here, we examined dihydrofolate reductase (DHFR), an enzyme that catalyzes hydride from C4′ of NADPH to C6 of 7,8-dihydrofolate (H2F). Despite many investigations of the mechanism of this reaction, the contribution of polarization of the π-bond of H2F in driving hydride transfer remains unclear. H2F was stereospecifically labeled with deuterium β to the reacting center, and β-deuterium kinetic isotope effects were measured. Our experimental results combined with analysis derived from QM/MM simulations reveal that hydride transfer is triggered by polarization at the C6 of H2F. The σ Cβ–H bonds contribute to the buildup of the cationic character during the chemical transformation, and hyperconjugation influences the formation of the transition state. Our findings provide key insights into the hydride transfer mechanism of the DHFR-catalyzed reaction, which is a target for antiproliferative drugs and a paradigmatic model in mechanistic enzymology.