The role of copper in particulate methane monooxygenase from Methylosinus trichosporium OB3b

The effect of metal ions on particulate methane monooxygenase (pMMO) was st udied. The pMMO activity in the membranes was partially inhibited by ethyle nediaminetetraacetic acid (EDTA), but remained more than 70% of the as-isol ated membranes. The activity of the EDTA-treated membranes was strongly inf luenced by the addition of metal ions. Among the metal ions, copper ion sti mulated the activity, indicating that copper was needed for the activity. W hen duroquinol and dioxygen were introduced to the EDTA-treated membranes, the electron spin resonance signal of copper did not change, suggesting tha t the copper cluster did not play as an electron transport and may have ano ther function, such as active site of pMMO or regulator of the activity. On the other hand, the iron signal (g = 5.98) decreased by the addition of du roquinol, dioxygen and acetylene, showing an iron atom is contained in the active site of pMMO. (C) 1999 Elsevier Science B.V. All rights reserved.