Information on EC 1.7.2.6 - hydroxylamine dehydrogenase

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The enzyme appears in viruses and cellular organisms

EC NUMBER
COMMENTARY hide
1.7.2.6
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RECOMMENDED NAME
GeneOntology No.
hydroxylamine dehydrogenase
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REACTION
REACTION DIAGRAM
COMMENTARY hide
ORGANISM
UNIPROT
LITERATURE
hydroxylamine + 3 ferricytochrome c = nitric oxide + 3 ferrocytochrome c + 3 H+
show the reaction diagram
(2)
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hydroxylamine + H2O + 4 ferricytochrome c = nitrite + 4 ferrocytochrome c + 5 H+
show the reaction diagram
(1)
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PATHWAY
BRENDA Link
KEGG Link
MetaCyc Link
ammonia oxidation I (aerobic)
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nitrifier denitrification
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nitrate assimilation
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Nitrogen metabolism
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Microbial metabolism in diverse environments
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SYSTEMATIC NAME
IUBMB Comments
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 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 produce nitric oxide as well [2].
GENERAL INFORMATION
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
physiological function
SUBSTRATE
PRODUCT                       
REACTION DIAGRAM
ORGANISM
UNIPROT
COMMENTARY
(Substrate) hide
LITERATURE
(Substrate)
COMMENTARY
(Product) hide
LITERATURE
(Product)
Reversibility
r=reversible
ir=irreversible
?=not specified
hydroxylamine + 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide + H2O
nitrite + ?
show the reaction diagram
hydroxylamine + ferricyanide
nitrite + ferrocyanide + H+
show the reaction diagram
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more than 90% of added hydroxylamine is oxidized to nitrite within 10 min when 10times as much ferricyanide as hydroxylamine is added
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?
hydroxylamine + ferricytochrome c + H2O
nitrite + ferrocytochrome c + H+
show the reaction diagram
hydroxylamine + ferricytochrome c554
nitric oxide + ferrocytochrome c554 + H+
show the reaction diagram
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-
?
hydroxylamine + ferricytochrome c554 + H2O
nitrite + ferrocytochrome c554 + H+
show the reaction diagram
hydroxylamine + H2O + 2 ferricyanide
nitrite + 2 ferrocyanide + 5 H+
show the reaction diagram
hydroxylamine + H2O + 2 ferricytochrome c-554
nitrite + 2 ferrocytochrome c + 5 H+
show the reaction diagram
hydroxylamine + N'-dinitroso-1,4-phenylenediamine
nitric oxide + ?
show the reaction diagram
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?
hydroxylamine + phenazine methosulfate + H2O
nitrite + ?
show the reaction diagram
NATURAL SUBSTRATES
NATURAL PRODUCTS
REACTION DIAGRAM
ORGANISM
UNIPROT
COMMENTARY
(Substrate) hide
LITERATURE
(Substrate)
COMMENTARY
(Product) hide
LITERATURE
(Product)
REVERSIBILITY
r=reversible
ir=irreversible
?=not specified
hydroxylamine + ferricytochrome c554 + H2O
nitrite + ferrocytochrome c554 + H+
show the reaction diagram
COFACTOR
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
IMAGE
cytochrome c
purified enzyme shows typical cytochrome-like absorption spectra, but with a peculiar peak at 468 nm in the reduced state that is due to a P460 moiety corresponding to a modified heme c molecule
INHIBITORS
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
IMAGE
cyanide
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active site inhibitor
KM VALUE [mM]
SUBSTRATE
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
IMAGE
0.0009
ferricyanide
pH 7.8, temperature not specified in the publication
0.0011
ferricytochrome c-554
source of substrate Nitrosococcus oceani, pH 7.8, temperature not specified in the publication
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TURNOVER NUMBER [1/s]
SUBSTRATE
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
IMAGE
111
ferricyanide
Nitrosococcus oceani
M5DCM0
pH 7.8, temperature not specified in the publication
3.4
ferricytochrome c-554
Nitrosococcus oceani
M5DCM0
source of substrate Nitrosococcus oceani, pH 7.8, temperature not specified in the publication
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SPECIFIC ACTIVITY [µmol/min/mg]
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
0.01
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crude lysate, in 0.1 M sodium glycine buffer at pH 8.8, temperature not specified in the publication
0.6
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after 60fold purification, in 0.1 M sodium glycine buffer at pH 8.8, temperature not specified in the publication
LOCALIZATION
ORGANISM
UNIPROT
COMMENTARY hide
GeneOntology No.
LITERATURE
SOURCE
PDB
SCOP
CATH
ORGANISM
UNIPROT
Nitrosomonas europaea (strain ATCC 19718 / NBRC 14298)
Nitrosomonas europaea (strain ATCC 19718 / NBRC 14298)
Nitrosomonas europaea (strain ATCC 19718 / NBRC 14298)
Nitrosomonas europaea (strain ATCC 19718 / NBRC 14298)
MOLECULAR WEIGHT
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
140000
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active enzyme, gel filtration
200000
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gel filtration
220000
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gel filtration
SUBUNITS
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
homotrimer
additional information
Crystallization/COMMENTARY
ORGANISM
UNIPROT
LITERATURE
hanging drop vapor diffusion method, using 2.4 M ammonium sulfate, 50 mM Tris-HCL, at pH 8.0
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to 2.1 A resolution. Heme P460 contains two covalent cross-links between the porphyrin and a Tyr residue. When purified from source, an unknown physiological HAO binding partner NE1300 is present within the crystal. Protein NE1300 may play a structural role in the ternary complex with cytochrome c554, the physiological electron acceptor of the enzyme
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OXIDATION STABILITY
ORGANISM
UNIPROT
LITERATURE
on exposure to air, the 100% reduced enzyme sample is oxidized within about 1 min
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394321
the enzyme is inactivated by incubation of 1 mM enzyme with a 5fold excess of peroxide for 1 h. The enzyme is also inactivated in the presence of H2O2
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719635
Purification/COMMENTARY
ORGANISM
UNIPROT
LITERATURE
ammonium sulfate precipitation
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ammonium sulfate precipitation, DEAE-cellulose column chromatography, and Sephadex G-200 gel filtration
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ammonium sulfate precipitation, octyl-Sepharose column chromatography, and Sephacryl S-200 gel filtration
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ammonium sulfate precipitation, Sepharose CL-6B column chromatography, DEAE-Sephacel gel filtration, octyl Sepharose column chromatography, and Sephadex G-100 gel filtration
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Cloned/COMMENTARY
ORGANISM
UNIPROT
LITERATURE
expressed in Escherichia coli DH5alpha cells
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EXPRESSION
ORGANISM
UNIPROT
LITERATURE
mRNA expression is upregulated in the presence of NH4+
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mRNA expression is upregulated in the presence of NH4+; there is some increase in the enzyme level only after 4 h incubation of starved Nitrosomonas europaea cells with 2 mM ammonia
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the enzyme level remains highly stable during ammonia starvation. The enzyme level shows no significant change when the cells are incubated with 0.2 mM ammonia for 60 min at 4C or 26C
there is some increase in the enzyme level only after 4 h incubation of starved Nitrosomonas europaea cells with 2 mM ammonia
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APPLICATION
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
analysis
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use of hydroxylamine oxidoreductase to differentiate Nitrosomonas spp. and to identify autotrophic ammonia oxidizing bacteria. The ensembled use of single strand confirmation polymorphism and HAO enzyme zymogram in fingerprinting AOB provide better resolution and evenness, contributing significantly in autotrophic ammonia oxidizing bacteria diversity studies