title: DFT study of the mechanism for methane hydroxylation by soluble methane monooxygenase (sMMO): effects of oxidation state, spin state, and coordination number.
abstract: The exact structure of the active site of intermediate Q, the methane-oxidizing species of soluble methane monooxygenase (sMMO), and the reaction mechanism of Q with methane molecule are still not fully clear. To gain further insights into the structure and reaction mechanism, five diiron models of Q that differ in shape, oxidation state, spin state, and coordination number of the two iron centers are studied. Different mechanisms in different spin states were explored. Density functional theory (DFT) calculations show that Fe(III)Fe(IV)(μ-O)(μ-OH) is more reactive than Fe(IV)(2)(μ-O)(2) in the oxygen-rich environment and that the reactivity of the active core of sMMO-Q is not enhanced by converting its oxo bridge into a terminal ligand. A four-coordinated diiron model is the most effective for methane hydroxylation. Both radical and non-radical intermediates are involved in the reactions for the four-coordinated diiron model.
authors.affiliation: Institute for Materials Chemistry and Engineering, and International Research Center for Molecular Systems, Kyushu University, Fukuoka 819-0395, Japan.
authors.forename: Shu-Ping
authors.initials: SP
authors.lastname: Huang
authors.forename: Yoshihito
authors.initials: Y
authors.lastname: Shiota
authors.forename: Kazunari
authors.initials: K
authors.lastname: Yoshizawa
mesh_terms: D020134:Catalytic Domain; D004583:Electrons; D006900:Hydroxylation; D007501:Iron / Q000737:chemistry; D008697:Methane / Q000737:chemistry / Q000378:metabolism*; D008956:Models, Chemical; D010084:Oxidation-Reduction; D010105:Oxygenases / Q000737:chemistry / Q000378:metabolism*; D011789:Quantum Theory; D013816:Thermodynamics
chemical_list: D007501:Iron; D010105:Oxygenases; C021555:methane monooxygenase; D008697:Methane