| Particulate methane monooxygenase | |||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
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| Identifiers | |||||||||||
| Symbol | pMMO | ||||||||||
| Pfam | PF02461 | ||||||||||
| InterPro | IPR003393 | ||||||||||
| OPM superfamily | 23 | ||||||||||
| OPM protein | 1yew | ||||||||||
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Methane monooxygenase (MMO) is an enzyme capable of oxidizing the C-H bond in methane as well as other alkanes.[1] Methane monooxygenase belongs to the class of oxidoreductase enzymes (EC 1.14.13.25).
There are two forms of MMO: the well-studied soluble form (sMMO) and the particulate form (pMMO).[2] 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.
The particulate methane monooxygenase and related ammonia monooxygenase are integral membrane proteins, occurring in methanotrophs and ammonia oxidisers, respectively, which are thought to be related.[3] These enzymes have a relatively wide substrate specificity and can catalyse the oxidation of a range of substrates including ammonia, methane, halogenated hydrocarbons, and aromatic molecules.[4] These enzymes are homotrimers composed of 3 subunits - A (InterPro: IPR003393), B (InterPro: IPR006833) and C (InterPro: IPR006980) and most contain two monocopper centers.[5][6]
The A subunit from Methylococcus capsulatus (Bath) resides primarily within the membrane and consists of 7 transmembrane helices and a beta-hairpin, which interacts with the soluble region of the B subunit. A conserved glutamate residue is thought to contribute to a metal center.[5]
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.[7] Notably, strictly anaerobic methanotrophs may also harbour methane monooxygenases, although there are critical mismatches in the gene which prevent common methanotroph-seeking primers from matching.[8]
- ^ Sazinsky MH, Lippard SJ (2015). "Chapter 6 Methane Monooxygenase: Functionalizing Methane at Iron and Copper". In Kroneck PM, Torres ME (eds.). Sustaining Life on Planet Earth: Metalloenzymes Mastering Dioxygen and Other Chewy Gases. Metal Ions in Life Sciences. Vol. 15. Springer. pp. 205–256. doi:10.1007/978-3-319-12415-5_6. ISBN 978-3-319-12414-8. PMID 25707469.
- ^ Ross MO, Rosenzweig AC (April 2017). "A tale of two methane monooxygenases". Journal of Biological Inorganic Chemistry. 22 (2–3): 307–319. doi:10.1007/s00775-016-1419-y. PMC 5352483. PMID 27878395.
- ^ Holmes AJ, Costello A, Lidstrom ME, Murrell JC (October 1995). "Evidence that particulate methane monooxygenase and ammonia monooxygenase may be evolutionarily related". FEMS Microbiology Letters. 132 (3): 203–208. doi:10.1111/j.1574-6968.1995.tb07834.x. PMID 7590173.
- ^ Arp DJ, Sayavedra-Soto LA, Hommes NG (October 2002). "Molecular biology and biochemistry of ammonia oxidation by Nitrosomonas europaea". Archives of Microbiology. 178 (4): 250–255. Bibcode:2002ArMic.178..250A. doi:10.1007/s00203-002-0452-0. PMID 12209257. S2CID 27432735.
- ^ a b Lieberman RL, Rosenzweig AC (March 2005). "Crystal structure of a membrane-bound metalloenzyme that catalyses the biological oxidation of methane". Nature. 434 (7030): 177–182. Bibcode:2005Natur.434..177L. doi:10.1038/nature03311. PMID 15674245. S2CID 30711411.
- ^ Ross MO, MacMillan F, Wang J, Nisthal A, Lawton TJ, Olafson BD, et al. (May 2019). "Particulate methane monooxygenase contains only mononuclear copper centers". Science. 364 (6440): 566–570. Bibcode:2019Sci...364..566R. doi:10.1126/science.aav2572. PMC 6664434. PMID 31073062.
- ^ Dalton H, Whittenbury R (August 1976). "The acetylene reduction technique as an assay for nitrogenase activity in the methane oxidizing bacterium Methylococcus capsulatus strain bath". Archives of Microbiology. 109 (1): 147–151. Bibcode:1976ArMic.109..147D. doi:10.1007/BF00425127. S2CID 21926661.
- ^ Luesken FA, Zhu B, van Alen TA, Butler MK, Diaz MR, Song B, et al. (June 2011). "pmoA Primers for detection of anaerobic methanotrophs". Applied and Environmental Microbiology. 77 (11): 3877–3880. Bibcode:2011ApEnM..77.3877L. doi:10.1128/AEM.02960-10. PMC 3127593. PMID 21460105.