KEGG   ENZYME: 1.7.3.6Help
Entry
EC 1.7.3.6                  Enzyme                                 

Name
hydroxylamine oxidase (cytochrome);
HAO (ambiguous);
hydroxylamine oxidoreductase (ambiguous);
hydroxylamine oxidase (misleading)
Class
Oxidoreductases;
Acting on other nitrogenous compounds as donors;
With oxygen as acceptor
BRITE hierarchy
Sysname
hydroxylamine:oxygen oxidoreductase
Reaction(IUBMB)
hydroxylamine + O2 = nitrite + H2O + H+ (overall reaction) [RN:R10230];
(1a) hydroxylamine + 2 ferricytochrome c = nitroxyl + 2 ferrocytochrome c + 2 H+ [RN:R10913];
(1b) nitroxyl + 2 ferrocytochrome c + O2 + H+ = nitrite + 2 ferricytochrome c + H2O (spontaneous) [RN:R10914]
Reaction(KEGG)
Substrate
hydroxylamine [CPD:C00192];
O2 [CPD:C00007];
ferricytochrome c [CPD:C00125];
nitroxyl [CPD:C20937];
ferrocytochrome c [CPD:C00126];
H+ [CPD:C00080]
Product
nitrite [CPD:C00088];
H2O [CPD:C00001];
H+ [CPD:C00080];
nitroxyl [CPD:C20937];
ferrocytochrome c [CPD:C00126];
ferricytochrome c [CPD:C00125]
Comment
The enzyme from the heterotrophic nitrifying bacterium Paracoccus denitrificans contains three to five non-heme, non-iron-sulfur iron atoms and interacts with cytochrome c556 and pseudoazurin [2,3]. Under anaerobic conditions in vitro only nitrous oxide is formed [3]. Presumably nitroxyl is released and combines with a second nitroxyl to give nitrous oxide and water. When oxygen is present, nitrite is formed.
History
EC 1.7.3.6 created 1972 as EC 1.7.3.4, part transferred 2013 to EC 1.7.3.6, modified 2015
Reference
1
  Authors
Kurokawa, M, Fukumori, Y and Yamanaka, T
  Title
A hydroxylamine - cytochrome c reductase occurs in the heterotrophic nitrifier Arthrobacter globiformis.
  Journal
Plant Cell Physiol 26 (1985) 1439-1442.
Reference
2  [PMID:8253206]
  Authors
Wehrfritz JM, Reilly A, Spiro S, Richardson DJ
  Title
Purification of hydroxylamine oxidase from Thiosphaera pantotropha. Identification of electron acceptors that couple heterotrophic nitrification to aerobic denitrification.
  Journal
FEBS. Lett. 335 (1993) 246-50.
Reference
3  [PMID:8920986]
  Authors
Moir JW, Wehrfritz JM, Spiro S, Richardson DJ
  Title
The biochemical characterization of a novel non-haem-iron hydroxylamine oxidase from Paracoccus denitrificans GB17.
  Journal
Biochem. J. 319 ( Pt 3) (1996) 823-7.
Reference
4  [PMID:9082922]
  Authors
Wehrfritz J, Carter JP, Spiro S, Richardson DJ
  Title
Hydroxylamine oxidation in heterotrophic nitrate-reducing soil bacteria and purification of a hydroxylamine-cytochrome c oxidoreductase from a Pseudomonas species.
  Journal
Arch. Microbiol. 166 (1996) 421-4.
Other DBs
ExplorEnz - The Enzyme Database: 
IUBMB Enzyme Nomenclature: 
ExPASy - ENZYME nomenclature database: 
BRENDA, the Enzyme Database: 
CAS: 
9075-43-8

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