Properties of the membranes containing the particulate methane monooxygenase from Methylosinus trichosporium OB3b.

The particulate methane monooxygenase (pMMO) from Methylosinus trichosporium OB3b was partially purified and characterized by measuring the effects of reducing agents and additives, and the stability of pMMO was studied. Duroquinol was a suitable reducing agent, and pMMO was stabilized by bovine serum albumin (BSA). Among the additives, the copper (II) ion stimulated pMMO at low concentration and inhibited at high concentration. The optimum conditions for pMMO activity were as follows: 45 degrees C, pH 6.5 and 55 mM 3-morpholinopropanesulfonic acid (MOPS) buffer, and the rate of propene epoxide formation was 13.6 nmol min-1 mg-1 protein. ESR spectra indicate that the copper cluster in the membrane fraction is reduced by duroquinol and oxidized by dioxygen. The result suggests that the copper cluster is contained in the active site of pMMO.