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EC 1.7.3.6 Details

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EC number

1.7.3.6

Accepted name

hydroxylamine oxidase (cytochrome)

Reaction

hydroxylamine + O₂ = nitrite + H₂O + H⁺ (overall reaction);;(1a) hydroxylamine + 2 ferricytochrome c = nitroxyl + 2 ferrocytochrome c + 2 H⁺;;(1b) nitroxyl + 2 ferrocytochrome c + O₂ + H⁺ = nitrite + 2 ferricytochrome c + H₂O (spontaneous)

Other name(s)

HAO (ambiguous), hydroxylamine oxidoreductase (ambiguous), hydroxylamine oxidase (misleading)

Systematic name

hydroxylamine:oxygen oxidoreductase

CAS registry number

9075-43-8

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

created 1972 as EC 1.7.3.4, part transferred 2013 to EC 1.7.3.6, modified 2015

EC Tree

1 Oxidoreductases

1.1 Acting on the CH-OH group of donors

1.1.1 With NAD⁺ or NADP⁺ as acceptor

1.1.2 With a cytochrome as acceptor

1.1.3 With oxygen as acceptor

1.1.4 With a disulfide as acceptor

1.1.5 With a quinone or similar compound as acceptor

1.1.7 With an iron-sulfur protein as acceptor

1.1.9 With a copper protein as acceptor

1.1.98 With other, known, physiological acceptors

1.1.98.1 alcohol dehydrogenase (azurin)

1.1.98.2 glucose-6-phosphate dehydrogenase (coenzyme-F₄₂₀)

1.1.98.3 decaprenylphospho-β-D-ribofuranose 2-dehydrogenase

1.1.98.4 F₄₂₀H₂:quinone oxidoreductase

1.1.98.5 secondary-alcohol dehydrogenase (coenzyme-F₄₂₀)

1.1.98.6 ribonucleoside-triphosphate reductase (formate)

1.1.98.7 serine-type anaerobic sulfatase-maturating enzyme

1.1.99 With unknown physiological acceptors

1.2 Acting on the aldehyde or oxo group of donors

1.3 Acting on the CH-CH group of donors

1.4 Acting on the CH-NH₂ group of donors

1.5 Acting on the CH-NH group of donors

1.6 Acting on NADH or NADPH

1.7 Acting on other nitrogenous compounds as donors

1.7.1 With NAD⁺ or NADP⁺ as acceptor

1.7.2 With a cytochrome as acceptor

1.7.3 With oxygen as acceptor

1.7.3.1 nitroalkane oxidase

1.7.3.2 acetylindoxyl oxidase

1.7.3.3 factor-independent urate hydroxylase

1.7.3.4 hydroxylamine oxidase

1.7.3.5 3-aci-nitropropanoate oxidase

1.7.3.6 hydroxylamine oxidase (cytochrome)

1.7.5 With a quinone or similar compound as acceptor

1.7.6 With a nitrogenous group as acceptor

1.7.7 With an iron-sulfur protein as acceptor

1.7.9 With a copper protein as acceptor

1.7.99 With unknown physiological acceptors

1.8 Acting on a sulfur group of donors

1.9 Acting on a heme group of donors

1.10 Acting on diphenols and related substances as donors

1.11 Acting on a peroxide as acceptor

1.12 Acting on hydrogen as donor

1.13 Acting on single donors with incorporation of molecular oxygen (oxygenases)

1.14 Acting on paired donors, with incorporation or reduction of molecular oxygen

1.15 Acting on superoxide as acceptor

1.16 Oxidizing metal ions

1.17 Acting on CH or CH₂ groups

1.18 Acting on iron-sulfur proteins as donors

1.19 Acting on reduced flavodoxin as donor

1.20 Acting on phosphorus or arsenic in donors

1.21 Catalysing the reaction X-H + Y-H = X-Y

1.21.1 With NAD⁺ or NADP⁺ as acceptor

1.21.3 With oxygen as acceptor

1.21.4 With a disulfide as acceptor

1.21.98 With other, known, physiological acceptors

1.21.99 With unknown physiological acceptors

1.22 Acting on halogen in donors

1.23 Reducing C-O-C group as acceptor

1.97 Other oxidoreductases

1.98 Enzymes using H₂ as reductant (deleted subclass)

1.98.1. undefined

1.99 Other enzymes using O₂ as oxidant (deleted subclass)