Two-step concerted mechanism for methane hydroxylation on the diiron active site of soluble methane monooxygenase.
Two-step concerted mechanism for methane hydroxylation on the diiron active site of soluble methane monooxygenase.
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DOI：
10.1016/s0162-0134(99)00201-9
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发表时间：
2000-01
影响因子：
3.9
通讯作者：
K. Yoshizawa
中科院分区：
文献类型：
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作者：
K. Yoshizawa
提出了一种在可溶性甲烷单加氧酶（sMMO）中间体 Q 上将甲烷转化为甲醇的新协同机制，其活性位点被认为涉及 Fe2(μ-O)2 金刚石核心。我们采用混合密度泛函理论 (DFT) 方法对裸 FeO+ 配合物和中间体 Q 的二铁模型的重要反应性进行了机理研究。二铁配合物上甲烷羟基化的反应途径与裸 FeO+ 配合物的气相反应基本相同。甲烷通过形成甲烷络合物而在双核铁模型上高度活化，其中配位不饱和铁在双核铁模型和底物甲烷之间的键合相互作用中发挥核心作用。通过四中心过渡态的 H 原子抽取以及通过三中心过渡态的 OH 和 CH3 基团的重组相继发生在双核铁氧物种上，导致形成对应于中间体 T 的甲醇络合物。这些电子过程以协调的方式发生。我们的 sMMO 甲烷羟基化机制不同于已被广泛接受的酶促烃羟基化的激进机制，尤其是细胞色素 P450 的羟基化机制。
A new concerted mechanism is proposed for the conversion of methane to methanol on intermediate Q of soluble methane monooxygenase (sMMO), the active site of which is considered to involve an Fe2(μ-O)2diamond core. A hybrid density functional theory (DFT) method is used for our mechanistic study on the important reactivity of the bare FeO+complex and a diiron model of intermediate Q. The reaction pathway for the methane hydroxylation on the diiron complex is essentially identical to that for the gas-phase reaction by the bare FeO+complex. Methane is highly activated on the dinuclear iron model through the formation of a methane complex, in which a coordinatively unsaturated iron plays a central role in the bonding interaction between the diiron model and substrate methane. A H atom abstraction via a four-centered transition state and a recombination of the OH and CH3groups via a three-centered transition state successively occur on the dinuclear iron–oxo species, leading to the formation of a methanol complex that corresponds to intermediate T. These electronic processes take place in a concerted manner. Our mechanism for methane hydroxylation by sMMO is different from the radical mechanism that has been widely accepted for enzymatic hydrocarbon hydroxylation, especially by cytochrome P450.