EC - Hydroxylamine dehydrogenase

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IntEnz Enzyme Nomenclature


Accepted name:
hydroxylamine dehydrogenase
Other names:
HAO [ambiguous]
hydroxylamine oxidoreductase [ambiguous]
hydroxylamine oxidase [misleading]
Systematic name:
hydroxylamine:ferricytochrome-c oxidoreductase




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 P460-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 produce nitric oxide as well [2].

Links to other databases

Enzymes and pathways: NC-IUBMB , BRENDA , ExplorEnz , ENZYME@ExPASy , KEGG , MetaCyc , UniPathway
Structural data: CSA , EC2PDB
CAS Registry Number: 9075-43-8


  1. Rees, M. K.
    Studies of the hydroxylamine metabolism of Nitrosomonas europaea. I. Purification of hydroxylamine oxidase.
    Biochemistry 7: 353-366 (1968). [PMID: 5758552]
  2. Hooper, A. B., Terry, K. R.
    Hydroxylamine oxidoreductase of Nitrosomonas. Production of nitric oxide from hydroxylamine.
    Biochim. Biophys. Acta 571: 12-20 (1979). [PMID: 497235]
  3. Hooper, A. B., Balny, C.
    Reaction of oxygen with hydroxylamine oxidoreductase of Nitrosomonas: fast kinetics.
    FEBS Lett. 144: 299-303 (1982). [PMID: 7117545]
  4. Lipscomb, J. D., Hooper, A. B.
    Resolution of multiple heme centers of hydroxylamine oxidoreductase from Nitrosomonas. 1. Electron paramagnetic resonance spectroscopy.
    Biochemistry 21: 3965-3972 (1982). [PMID: 6289867]
  5. Poret-Peterson, A. T., Graham, J. E., Gulledge, J., Klotz, M. G.
    Transcription of nitrification genes by the methane-oxidizing bacterium, Methylococcus capsulatus strain Bath.
    ISME J 2: 1213-1220 (2008). [PMID: 18650926]

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