Illustration of the enzyme methane monooxygenase hydroxylase in complex with the regulatory subunit DBL1 from the methanotrophic bacterium Methylosinus trichosporium. This is the soluble methane monooxygenase hydroxylase (sMMOH) form of this metalloenzyme, which is found in the cytoplasm and contains iron. It can catalyse a variety of reactions, particularly the conversion of methane to methanol. It is being investigated as a possible catalyst for utilising methane energy sources.