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-peroxoCu IICuII 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.
All Science Journal Classification (ASJC) codes
- Physical and Theoretical Chemistry
- Inorganic Chemistry