The intracellular location of methane mono-oxygenase (MMO) (soluble or particulate) in Methylosinus trichosporium OB3b is dependent on the availability of copper in the growth medium. Raising the Cuz+ concentration from 1 VM to 5 p~ effected a transition from soluble to particulate MMO activity, and changes in major cell polypeptides were observed on SDSpolyacrylamide gels. Organisms containing soluble MMO oxidized a wide range of substrates including n-alkanes, n-alkenes, aromatic and alicyclic compounds. By contrast, organisms containing particulate MMO did not oxidize aromatic or alicyclic compounds. These observations provide further evidence that the two types of MMO are fundamentally different.

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