The bioinorganic chemistry of the particulate methane monooxygenase from Methylococcus capsulatus (Bath) and methane activation from a biological perspective

By cultivating Methylococcus capsulatus (Bath) under methane stress conditions and high copper levels in the growth medium, we have been able to obtain membranes highly enriched in particulate methane monooxygenase (pMMO), exhibiting exceptional activity stability. Subsequently, purified and active pMMO can be obtained using protocols in which excess of reductants and deoxygenated conditions were maintained during membrane solubilization by dodecyl-;Biochemical investigations of the pMMO in situ reveal that the pMMO activity increases with increasing copper content and the enzyme activity from membranes obtained from cells grown at low copper levels can be stimulated further by the addition of copper ions to the assay medium. The bulk of the membrane-bound copper ions are associated primarily with the pMMO, which can exist in both Cu(II) and Cu(I) forms.;The alkane hydroxylation chemistry of the pMMO from Methylococcus capsulatus (Bath) was also investigated. Consistent with previous works, the pMMO is shown to be capable of oxidizing C5 hydrocarbon or less. The enzyme exhibits the highest reactivity toward methane and ethane. The oxidation rate of these substrates is one to two orders of magnitude faster than those of higher alkanes and alkenes. (Abstract shortened by UMI.)...