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首页> 外文期刊>The journal of physical chemistry, B. Condensed matter, materials, surfaces, interfaces & biophysical >Insights into the Reaction Mechanism of Aromatic Ring Cleavage by Homogentisate Dioxygenase: A Quantum Mechanical/Molecular Mechanical Study
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Insights into the Reaction Mechanism of Aromatic Ring Cleavage by Homogentisate Dioxygenase: A Quantum Mechanical/Molecular Mechanical Study

机译:均草酸酯双加氧酶对芳香环裂解反应机理的认识:量子力学/分子力学研究

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摘要

To elucidate the reaction mechanism of the ring cleavage of homogentisate by homogentisate dioxygenase, quantum mechanical/molecular mechanical (QM/MM) calculations were carried out by using two systems in different protonation states of the substrate C-2 hydroxyl group. When the substrate C-2 hydroxyl group is ionized (the ionized pathway), the superoxo attack on the substrate is the rate-limiting step in the catalytic cycle, with a barrier of 15.9 kcal/mol. Glu396 was found to play an important role in stabilizing the bridge species and its O-O cleavage product by donating a proton via a hydrogen-bonded water molecule. When the substrate C-2 hydroxyl group is not ionized (the nonionized pathway), the O-O bond cleavage of the bridge species is the rate-limiting step, with a barrier of 15.3 kcal/mol. The QM/MM-optimized geometries for the dioxygen and alkylperoxo complexes using the nonionized model (for the C-2 hydroxyl group) are in agreement with the experimental crystal structures, group is more likely to be nonionized. suggesting that the C-2 hydroxyl group is more likely to be nonionized.
机译:为了阐明高纯酸双加氧酶对高纯酸环裂解的反应机理,通过使用两个系统在底物C-2羟基的不同质子化状态下进行了量子力学/分子机械(QM / MM)计算。当底物C-2羟基被离子化(离子化途径)时,对底物的超氧进攻是催化循环中的限速步骤,其势垒为15.9 kcal / mol。发现Glu396在通过氢键水分子贡献质子的过程中,在稳定桥物种及其O-O裂解产物中起着重要作用。当底物C-2羟基未电离时(非电离途径),桥键物种的O-O键裂解是限速步骤,势垒为15.3 kcal / mol。使用非离子化模型(针对C-2羟基)对双氧和烷基过氧配合物进行QM / MM优化的几何形状与实验晶体结构相符,该基团更可能被非离子化。提示C-2羟基更可能被非离子化。

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