IUBMB Enzyme Nomenclature


Accepted name: hydroxylamine dehydrogenase

Reaction: hydroxylamine + H2O + 4 ferricytochrome c = nitrite + 4 ferrocytochrome c + 5 H+

Other name(s): HAO (ambiguous); hydroxylamine oxidoreductase (ambiguous); hydroxylamine oxidase (misleading)

Systematic name: hydroxylamine:ferricytochrome-c oxidoreductase (nitrite-forming)

Comments: The enzymes from the nitrifying bacterium Nitrosomonas europaea [1,4] and the methylotrophic bacterium Methylococcus capsulatus [5] are hemoproteins with seven c-type hemes and one specialized P-460-type heme per subunit. The enzyme converts hydroxylamine to nitrite via an enzyme-bound nitroxyl intermediate [3]. While nitrite is the main product, the enzyme from Nitrosomonas europaea can also produce nitric oxide by catalysing the activity of EC, hydroxylamine oxidase [2].

Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, PDB, CAS registry number: 9075-43-8


1. Rees, M. Studies of the hydroxylamine metabolism of Nitrosomonas europaea. I. Purification of hydroxylamine oxidase. Biochemistry 7 (1968) 353-366. [PMID: 5758552]

2. Hooper, A.B. and Terry, K.R. Hydroxylamine oxidoreductase of Nitrosomonas. Production of nitric oxide from hydroxylamine. Biochim. Biophys. Acta 571 (1979) 12-20. [PMID: 497235]

3. Hooper, A.B. and Balny, C. Reaction of oxygen with hydroxylamine oxidoreductase of Nitrosomonas: fast kinetics. FEBS Lett. 144 (1982) 299-303. [PMID: 7117545]

4. Lipscomb, J.D. and Hooper, A.B. Resolution of multiple heme centers of hydroxylamine oxidoreductase from Nitrosomonas. 1. Electron paramagnetic resonance spectroscopy. Biochemistry 21 (1982) 3965-3972. [PMID: 6289867]

5. Poret-Peterson, A.T., Graham, J.E., Gulledge, J. and Klotz, M.G. Transcription of nitrification genes by the methane-oxidizing bacterium, Methylococcus capsulatus strain Bath. ISME J. 2 (2008) 1213-1220. [PMID: 18650926]

[EC created 1972 as EC, part transferred 2012 to EC, modifed 2021, modified 2021]

Return to EC 1.7.2 home page
Return to EC 1.7 home page
Return to EC 1 home page
Return to Enzymes home page
Return to IUBMB Biochemical Nomenclature home page