PROPERTIES OF THE METHANE MONO-OXYGENASE FROM EXTRACTS OF METHYLOSINUS-TRICHOSPORIUM OB3B AND EVIDENCE FOR ITS SIMILARITY TO THE ENZYME FROM METHYLOCOCCUS-CAPSULATUS (BATH)

The methane mono‐oxygenase from Methylosinus 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 potassium cyanide, amytal, carbon monoxide 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 two components by ion‐exchange chromatography. Activity could be restored to one of the components on addition of purified components from Methylococcus 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. Copyright © 1979, Wiley Blackwell. All rights reserved