Role of Tyrosine Residue in Methane Activation at the Dicopper Site of Particulate Methane Monooxygenase: A Density Functional Theory Study

• Published in: Inorganic chemistry Vol. 52; no. 14; pp. 7907 - 7917
• Main Authors: Shiota, Yoshihito, Juhász, Gergely, Yoshizawa, Kazunari
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 15.07.2013
• Subjects: Catalytic Domain; Copper - chemistry; Copper - metabolism; Methane - metabolism; Methylocystaceae - chemistry; Methylocystaceae - enzymology; Methylosinus - chemistry; Methylosinus - enzymology; Models, Molecular; Oxygenases - chemistry; Oxygenases - metabolism
• ISSN: 0020-1669; 1520-510X
• DOI: 10.1021/ic400417d

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)CuIICuIII 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-η2:η2-peroxoCuIICuII species and the resultant (μ-oxo)(μ-hydroxo)CuIICuIII species can hydroxylate methane. This species for methane hydroxylation is more favorable in reactivity than the bis(μ-oxo)CuIIICuIII 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-η2:η2-peroxoCuIICuII species to form the reactive (μ-oxo)(μ-hydroxo)CuIICuIII 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.