Hydrogen peroxide as an effecter on the inactivation of particulate methane monooxygenase under aerobic conditions

Particulate methane monooxygenase (pMMO), a copper-containing membrane protein, catalyzes methane hydroxylation under aerobic conditions. We found that the activity of pMMO was increased by catalase, implying that hydrogen peroxide (H2O2) is generated by pMMO with duroquinol, an electron donor for pMMO, and that the generated H2O2 inhibits pMMO activity. In addition, reversible inhibition of pMMO with H2O2 was observed upon treatment of pMMO with H2O2 followed by the addition of catalase, and H2O2 formation by pMMO with duroquinol was detected using a fluorescence probe. The redox behavior of type 2 copper in pMMO measured by the electron paramagnetic resonance revealed that H2O2 re-oxidizes the type 2 copper in pMMO reduced with duroquinol.