Electron transfer reactions in the soluble methane monooxygenase of Methylococcus capsulatus (Bath).
Aerobic stopped-flow experiments have confirmed that component C is the methane monooxygenase component responsible for interaction with NADH. Reduction of component C by NADH is not the rate-limiting step for component C in the methane monooxygenase reaction. Removal and reconstitution of the redox centres of component C suggest a correlation between the presence of the FAD and Fe2S2 redox centres and NADH: acceptor reductase activity and methane monooxygenase activity respectively, consistent with the order of electron flow: NADH----FAD----Fe2S2----component A. This order suggests that component C functions as a 2e-1/1e-1 transformase, splitting electron pairs from NADH for transfer to component A via the one-electron-carrying Fe2S2 centre. Electron transfer has been demonstrated between the reductase component, component C and the oxygenase component, component A, of the methane monooxygenase complex from Methylococcus capsulatus (Bath) by three separate methods. This intermolecular electron transfer step is not rate-determining for the methane monooxygenase reaction. Intermolecular electron transfer was independent of component B, the third component of the methane monooxygenase. Component B is required to switch the oxidase activity of component A to methane mono-oxygenase activity, suggesting that the role of component B is to couple substrate oxidation to electron transfer, via the methane monooxygenase components.
D004563:Electrochemistry; D004579:Electron Transport; D005182:Flavin-Adenine Dinucleotide / Q000378:metabolism; D007506:Iron-Sulfur Proteins / Q000378:metabolism; D008772:Methylococcaceae / Q000201:enzymology*; D009243:NAD / Q000378:metabolism; D010084:Oxidation-Reduction; D010105:Oxygenases / Q000378:metabolism*; D011485:Protein Binding; D012995:Solubility; D013053:Spectrophotometry
D007506:Iron-Sulfur Proteins; D009243:NAD; D005182:Flavin-Adenine Dinucleotide; D010105:Oxygenases; C021555:methane monooxygenase