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Particulate methane monooxygenase contains only mononuclear copper centers

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Science  10 May 2019:
Vol. 364, Issue 6440, pp. 566-570
DOI: 10.1126/science.aav2572

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How many metals to oxidize methane?

Methane is an important fuel, but there are few direct transformations to partially oxidized products. Bacteria use metalloenzymes to catalyze methane oxidation to methanol, a reaction of industrial interest. Understanding the metal sites that enable this reaction may inspire new biomimetic catalysts. Ross et al. used spectroscopic measurements to assign two monocopper sites in the enzyme particulate methane monooxygenase. These results differ in part from previous proposals for the location and nuclearity of the metal sites and will prompt rethinking about how this metalloenzyme catalyzes methane oxidation.

Science, this issue p. 566

Abstract

Bacteria that oxidize methane to methanol are central to mitigating emissions of methane, a potent greenhouse gas. The nature of the copper active site in the primary metabolic enzyme of these bacteria, particulate methane monooxygenase (pMMO), has been controversial owing to seemingly contradictory biochemical, spectroscopic, and crystallographic results. We present biochemical and electron paramagnetic resonance spectroscopic characterization most consistent with two monocopper sites within pMMO: one in the soluble PmoB subunit at the previously assigned active site (CuB) and one ~2 nanometers away in the membrane-bound PmoC subunit (CuC). On the basis of these results, we propose that a monocopper site is able to catalyze methane oxidation in pMMO.

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