Properties of the Methane Mono‐oxygenase from Extracts of Methylosinus trichosporium OB3b and Evidence for Its Similarity to the Enzyme from Methylococcus capsulatus (Bath)

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Abstract
The methane mono-oxygenase from M. trichosporium OB3b was soluble. The only suitable electron donor was NAD(P)H, neither sodium L-ascorbate nor electrons derived from the oxidation of methanol could substitute for NAD(P)H. Evidence is presented for the existence of an NAD+-linked formaldehyde dehydrogenase. Mono-oxygenase activity was not inhibited by a range of potential inhibitors including KCN, amytal, CO or various metal-chelating agents, although 8-hydroxyquinoline and ethyne were effective in this respect. Although the enzyme preparations were unstable on storage, the crude extract could be resolved into 2 components by ion-exchange chromatography. Activity could be restored to 1 of the components on addition of purified components from M. capsulatus (Bath). Cross-reactivity of mono-oxygenase components and other similarities between the enzymes from M. trichosporium and M. capsulatus are discussed. The properties of the M. trichosporium methane mono-oxygenase reported here are contrasted with the properties of the same enzyme reported by others.