Institute for Materials Chemistry and Engineering and International Research Center for Molecular System, Kyushu University, Fukuoka 819-0395, Japan.
Inorg Chem. 2013 Jul 15;52(14):7907-17. doi: 10.1021/ic400417d. Epub 2013 Jun 28.
Methane hydroxylation at the dinuclear copper site of particulate methane monooxygenase (pMMO) is studied by using density functional theory calculations. The electronic, structural, and reactivity properties of a possible dinuclear copper species (μ-oxo)(μ-hydroxo)Cu(II)Cu(III) are discussed with respect to the C-H bond activation of methane. We propose that the tyrosine residue in the second coordination sphere of the dicopper site donates an H atom to the μ-η(2):η(2)-peroxoCu(II)Cu(II) species and the resultant (μ-oxo)(μ-hydroxo)Cu(II)Cu(III) species can hydroxylate methane. This species for methane hydroxylation is more favorable in reactivity than the bis(μ-oxo)Cu(III)Cu(III) species. The H-atom transfer or proton-coupled electron transfer from the tyrosine residue can reasonably induce the O-O bond dissociation of the μ-η(2):η(2)-peroxoCu(II)Cu(II) species to form the reactive (μ-oxo)(μ-hydroxo)Cu(II)Cu(III) species, which is expected to be an active species for the conversion of methane to methanol at the dicopper site of pMMO. The rate-determining step for the methane hydroxylation is the C-H cleavage, which is in good agreement with experimental KIE values reported so far.
采用密度泛函理论计算研究了颗粒态甲烷单加氧酶（pMMO）双核铜位上的甲烷羟化反应。讨论了双核铜物种（μ-氧代）（μ-羟代）Cu（II）Cu（III）的电子、结构和反应性性质，以及其对甲烷 C-H 键的活化。我们提出双核铜位的第二配位层中的酪氨酸残基向μ-η（2）：η（2）-过氧代 Cu（II）Cu（II）物种供氢原子，得到的（μ-氧代）（μ-羟代）Cu（II）Cu（III）物种可以羟化甲烷。与双（μ-氧代）Cu（III）Cu（III）物种相比，该物种在反应性方面更有利于甲烷羟化。来自酪氨酸残基的 H 原子转移或质子偶联电子转移可以合理地诱导μ-η（2）：η（2）-过氧代 Cu（II）Cu（II）物种的 O-O 键断裂，形成活性（μ-氧代）（μ-羟代）Cu（II）Cu（III）物种，这有望成为 pMMO 双核铜位上甲烷转化为甲醇的活性物种。甲烷羟化的速率决定步骤是 C-H 键的断裂，这与迄今为止报道的实验 KIE 值非常吻合。
