Hydroxylamine oxidoreductase
| Hydroxylamine Oxidoreductase | |||||||||
|---|---|---|---|---|---|---|---|---|---|
| Identifiers | |||||||||
| EC no. | 1.7.3.4 | ||||||||
| CAS no. | 9075-43-8 | ||||||||
| Databases | |||||||||
| IntEnz | IntEnz view | ||||||||
| BRENDA | BRENDA entry | ||||||||
| ExPASy | NiceZyme view | ||||||||
| KEGG | KEGG entry | ||||||||
| MetaCyc | metabolic pathway | ||||||||
| PRIAM | profile | ||||||||
| PDB structures | RCSB PDB PDBe PDBsum | ||||||||
| Gene Ontology | AmiGO / QuickGO | ||||||||
| |||||||||
Hydroxylamine oxidoreductase (HAO) is an enzyme found in the prokaryotic genus Nitrosomonas. It plays a critically important role in the biogeochemical nitrogen cycle as part of the metabolism of ammonia-oxidizing bacteria.
The substrate is hydroxylamine (), a chemical produced biologically by the enzyme Ammonia monooxygenase. The products of the catalyzed reaction are debated, but recent work shows compelling evidence for the production of nitric oxide.[1]
Structural studies
[edit]Crystallographic methods show that HAO (PDB code: 1FGJ) is a cross-linked trimer of polypeptides containing 24 heme cofactors.[2][3]
Reactivity
[edit]For many decades the enzyme was thought to catalyze the following reaction:[4]
Recent work in the field, however, reveals that this enzyme catalyzes an entirely different reaction:[1]
Subsequent oxidation of the nitric oxide to nitrite caused by reaction with oxygen accounts for the reactivity previous described by Hooper et al.
Environmental Impact
[edit]Nitric oxide, the product of HAO catalysis, is a potent greenhouse gas.[5] Additionally, the oxidized product of nitric oxide in the presence of oxygen is nitrite - a common pollutant in agricultural run-off.
References
[edit]- ^ a b Caranto, Jonathan D.; Lancaster, Kyle M. (2017-07-17). "Nitric oxide is an obligate bacterial nitrification intermediate produced by hydroxylamine oxidoreductase". Proceedings of the National Academy of Sciences. 114 (31): 8217–8222. Bibcode:2017PNAS..114.8217C. doi:10.1073/pnas.1704504114. ISSN 0027-8424. PMC 5547625. PMID 28716929.
- ^ Cedervall, Peder; Hooper, Alan B.; Wilmot, Carrie M. (2013-09-10). "Structural Studies of Hydroxylamine Oxidoreductase Reveal a Unique Heme Cofactor and a Previously Unidentified Interaction Partner". Biochemistry. 52 (36): 6211–6218. doi:10.1021/bi400960w. ISSN 0006-2960. PMID 23952581.
- ^ Igarashi, N.; Moriyama, H.; Fujiwara, T.; Fukumori, Y.; Tanaka, N. (April 1997). "The 2.8 A structure of hydroxylamine oxidoreductase from a nitrifying chemoautotrophic bacterium, Nitrosomonas europaea". Nature Structural Biology. 4 (4): 276–284. doi:10.1038/nsb0497-276. ISSN 1072-8368. PMID 9095195. S2CID 1028628.
- ^ Hendrich, Michael P.; Logan, Michael; Andersson, Kristoffer K.; Arciero, Dave M.; Lipscomb, John D.; Hooper, Alan B. (1994-12-01). "The Active Site of Hydroxylamine Oxidoreductase from Nitrosomonas: Evidence for a New Metal Cluster in Enzymes". Journal of the American Chemical Society. 116 (26): 11961–11968. doi:10.1021/ja00105a041. ISSN 0002-7863.
- ^ Montzka, S. A.; Dlugokencky, E. J.; Butler, J. H. (2011). "Non-CO2 greenhouse gases and climate change". Nature. 476 (7358): 43–50. doi:10.1038/nature10322. PMID 21814274. S2CID 205225911.
- Hooper AB, Balny C (1982). "Reaction of oxygen with hydroxylamine oxidoreductase of Nitrosomonas: fast kinetics". FEBS Lett. 144 (2): 299–303. Bibcode:1982FEBSL.144..299H. doi:10.1016/0014-5793(82)80658-3. PMID 7117545. S2CID 9726167.
- Lipscomb JD, Hooper AB (1982). "Resolution of multiple heme centers of hydroxylamine oxidoreductase from Nitrosomonas. 1. Electron paramagnetic resonance spectroscopy". Biochemistry. 21 (17): 3965–72. doi:10.1021/bi00260a010. PMID 6289867.
- Rees MK (1968). "Studies of the hydroxylamine metabolism of Nitrosomonas europaea. I Purification of hydroxylamine oxidase". Biochemistry. 7 (1): 353–66. doi:10.1021/bi00841a045. PMID 5758552.
