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Methane monooxygenase, or MMO, is an enzyme capable of oxidizing the C-H bond in methane as well as other alkanes. Methane monooxygenase belongs to the class of oxidoreductase enzymes (). There are two well-studied forms of MMO: the soluble form (sMMO) and the particulate form (pMMO). The active site in sMMO contains a di-iron center bridged by an oxygen atom (Fe-O-Fe), whereas the active site in pMMO utilizes copper. Structures of both proteins have been determined by X-ray crystallography; however, the location and mechanism of the active site in pMMO is still poorly understood and is an area of active research.
Methane monooxygenases are found in methanotrophic bacteria, a class of bacteria that exist at the interface of aerobic (oxygen-containing) and anaerobic (oxygen-devoid) environments. One of the more widely studied bacteria of this type is Methylococcus capsulatus (Bath). This bacterium was discovered in the hot springs of Bath, England.
Soluble Methane Monooxygenase (sMMO)
Soluble methane monooxygenase (sMMO) has been found to be capable of oxidizing a wide range of carbon-containing substrates. These include halogenated aliphatic compounds such as trichloroethylene (TCE), a significant groundwater pollutant. Degradation of TCE by pure methanotrophic cultures has been well documented. The rapid oxidation and degradation of TCE by sMMO and the ready availability of natural gas as a growth substrate make methanotrophs attractive for bioremediation applications.
The molecule is a multicomponent enzyme consisting of a hydroxylase component (B) and two reductase components (A and C). All three proteins are required for monooxygenase activity. Protein B is a single subunit protein devoid of prosthetic groups. It regulates sMMO activity, possessing the capacity to convert the enzyme from an oxidase to an oxygenase. Proteins A and C together catalyze the reduction of molecular oxygen to water, a reaction prevented by protein B.
See also
References
- J.J.R. Fraústo da Silva and R.J.P. Williams, The biological chemistry of the elements: The inorganic chemistry of life, 2nd Edition, Oxford University Press, 2001, ISBN 0-19-850848-4
"Methane monooxygenase"