Insights into the (Superoxo)Fe(III)Fe(III) Intermediate and Reaction Mechanism ofmyo-Inositol Oxygenase: DFT and ONIOM(DFT:MM) Study,Journal of the American Chemical Society

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Insights into the (Superoxo)Fe(III)Fe(III) Intermediate and Reaction Mechanism ofmyo-Inositol Oxygenase: DFT and ONIOM(DFT:MM) Study
Journal of the American Chemical Society ( IF 14.4 ) Pub Date : 2009-12-02 , DOI: 10.1021/ja905296w
Hajime Hirao ₁ , Keiji Morokuma ₁

Affiliation

The (superoxo)Fe(III)Fe(III) reactive species and the catalytic reaction mechanism of a diiron enzyme, myo-inositol oxygenase (MIOX), were theoretically investigated by means of density functional theory (DFT) and ONIOM quantum mechanical/molecular mechanical (QM/MM) approaches. The ground state of the (superoxo)Fe(III)Fe(III) intermediate was shown to have a side-on coordination geometry and an S = 1/2 spin state, wherein the two iron sites are antiferromagnetically coupled while the superoxide site and the nearest iron are ferromagnetically coupled. A full reaction pathway leading to a D-glucuronate product from myo-inositol was proposed based on ONIOM computational results. Two major roles of the enzyme surrounding during the catalytic reaction were identified. One is to facilitate the initial H-abstraction step, and the other is to restrict the movement of the substrate via H-bonding interactions in order to avoid unwanted side reactions. In our proposed mechanism, O-O bond cleavage has the highest barrier, thus constituting the rate-limiting step of the reaction. The unique role of the bridging hydroxide ligand as a catalytic base was also identified.

中文翻译：

深入了解肌醇氧化酶的 (Superoxo)Fe(III)Fe(III) 中间体和反应机制：DFT 和 ONIOM(DFT:MM) 研究

通过密度泛函理论 (DFT) 和 ONIOM 量子力学/分子动力学理论研究了 (superoxo)Fe(III)Fe(III) 反应物种和二铁酶肌醇加氧酶 (MIOX) 的催化反应机制机械 (QM/MM) 方法。(superoxo)Fe(III)Fe(III) 中间体的基态显示出具有侧面配位几何形状和 S = 1/2 自旋态，其中两个铁位点反铁磁耦合，而超氧化物位点和最近的铁是铁磁耦合的。基于 ONIOM 计算结果提出了从肌醇生成 D-葡萄糖醛酸产物的完整反应途径。鉴定了催化反应过程中酶周围的两个主要作用。一是促进初始 H 抽象步骤，另一个是通过氢键相互作用限制底物的运动，以避免不必要的副反应。在我们提出的机制中，OO 键断裂具有最高的势垒，因此构成了反应的限速步骤。还确定了桥连氢氧化物配体作为催化碱的独特作用。

更新日期：2009-12-02

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