Information on EC 1.7.3.6 - hydroxylamine oxidase (cytochrome)

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The enzyme appears in viruses and cellular organisms

EC NUMBER
COMMENTARY hide
1.7.3.6
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RECOMMENDED NAME
GeneOntology No.
hydroxylamine oxidase (cytochrome)
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REACTION
REACTION DIAGRAM
COMMENTARY hide
ORGANISM
UNIPROT
LITERATURE
hydroxylamine + 2 ferricytochrome c = nitroxyl + 2 ferrocytochrome c + 2 H+
show the reaction diagram
(1a)
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hydroxylamine + O2 = nitrite + H2O + H+
show the reaction diagram
overall reaction
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nitroxyl + 2 ferrocytochrome c + O2 + H+ = nitrite + 2 ferricytochrome c + H2O
show the reaction diagram
spontaneous
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REACTION TYPE
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
dehydrogenation
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oxidation
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redox reaction
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reduction
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SYSTEMATIC NAME
IUBMB Comments
hydroxylamine:oxygen oxidoreductase
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.
CAS REGISTRY NUMBER
COMMENTARY hide
9075-43-8
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ORGANISM
COMMENTARY hide
LITERATURE
UNIPROT
SEQUENCE DB
SOURCE
strain YNSRA
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Manually annotated by BRENDA team
strain YNSRA
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Manually annotated by BRENDA team
strain ENI-11
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Manually annotated by BRENDA team
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Manually annotated by BRENDA team
SUBSTRATE
PRODUCT                       
REACTION DIAGRAM
ORGANISM
UNIPROT
COMMENTARY
(Substrate) hide
LITERATURE
(Substrate)
COMMENTARY
(Product) hide
LITERATURE
(Product)
Reversibility
r=reversible
ir=irreversible
?=not specified
hydrazine + ferricytochrome c
? + ferrocytochrome c
show the reaction diagram
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?
hydrazine + O2
N2 + H2O
show the reaction diagram
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-
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?
hydrazine + phenazine methosulfate
N2 + reduced phenazine methosulfate
show the reaction diagram
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?
hydroxylamine + ferricytochrome c
nitrite + ferrocytochrome
show the reaction diagram
hydroxylamine + ferricytochrome c
nitrite + ferrocytochrome c + H+
show the reaction diagram
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horse heart cytochrome. Under aerobic assay conditions nitrite is the major reaction product but N2O is also detected at low levels. Under anaerobic conditions no nitrite is produced but N2O is detected, though at non-stoichiometric levels. The production of nitrite by Paracoccus denitrificans hydroxylamine oxidase is an oxygen-dependent reaction
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?
hydroxylamine + ferricytochrome c550
nitrite + ferrocytochrome c550 + H+
show the reaction diagram
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under aerobic assay conditions nitrite is the major reaction product but N2O is also detected at low levels. Under anaerobic conditions no nitrite is produced but N2O is detected, though at non-stoichiometric levels. The production of nitrite by Paracoccus denitrificans hydroxylamine oxidase is an oxygen-dependent reaction
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?
hydroxylamine + ferricytochrome c551
nitrite + ferrocytochrome c551 + H+
show the reaction diagram
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?
hydroxylamine + methyl viologen + H+
NH4+ + reduced methyl viologen + H2O
show the reaction diagram
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ir
hydroxylamine + O2
nitrite + H2O
show the reaction diagram
hydroxylamine + O2
nitrite + H2O + H+
show the reaction diagram
hydroxylamine + O2
NO + N2O
show the reaction diagram
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?
hydroxylamine + O2 + ferricytochrome c
nitrite + H2O + ferrocytochrome c + H+
show the reaction diagram
hydroxylamine + O2 + horse heart ferricytochrome c
nitrite + H2O + horse heart ferrocytochrome c + H+
show the reaction diagram
hydroxylamine + phenazine methosulfate
nitrite + ?
show the reaction diagram
hydroxylamine + pseudoazurin
nitrite + reduced pseudoazurin
show the reaction diagram
hydroxylamine + Ru(NH3)63++ H+
nitric oxide + Ru(NH3)62+ + H+
show the reaction diagram
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ir
nitrite + methyl viologen + H+
NH4+ + reduced methyl viologen + H2O
show the reaction diagram
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HAO acts like a cytochrome c nitrite reductase, which catalyzes the six-electron reduction of nitrite to NH4+ by reduced methyl viologen
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?
pyrogallol + O2
?
show the reaction diagram
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?
additional information
?
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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 + O2
nitrite + H2O
show the reaction diagram
hydroxylamine + O2
nitrite + H2O + H+
show the reaction diagram
COFACTOR
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
IMAGE
cytochrome c554
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heme c
additional information
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METALS and IONS
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
Ce(NH4)2(NO3)6
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0.1 mM, stimulates the rate of oxidation of NH2OH 2.6-fold and inhibits production of HNO2 by 40%
Fe2+
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the enzyme is activated 6fold and 21fold by 0.01 mM and 0.1 mM ferrous ions, respectively
Iron
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contains 3-5 nonhaem, non-iron-sulfur iron atoms as prosthetic groups, predominantly coordinated by carboxylate ligands
Mn2+
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0.001 mM, stimulation of NH2OH utilization, stimulation at pH 6 and pH 9 is approximately 40% greater than at pH 7 and pH 8
additional information
INHIBITORS
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
IMAGE
2',2'-dipyridyl
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50% inhibition at 0.1 mM
8-hydroxyquinoline
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50% inhibition at 0.2 mM
azide
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50% inhibition at 3.2 mM
Cd2+
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decreases in hydroxylamine oxidoreductase-specific oxygen uptake rate followed by a recovery of hydroxylamine oxidoreductase-specific oxygen uptake rate above steady-state levels do occur upon exposure to Cd2+ concentrations of 0.03 mM and greater
Ce(NH4)2(NO3)6
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0.1 mM, stimulates the rate of oxidation of NH2OH 2.6-fold and inhibits production of HNO2 by 40%
Co(NO3)2
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0.1 mM, 70% inhibition of the rate of nitrite synthesis
cyanide
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the cyanide-sensitive form of the enzyme exists only during turnover
diethyldithiocarbamate
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inhibition of nitrate production at 0.1 mM
hydrazine
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50% inhibition at 0.1 mM
hydroxyethyl-hydrazine
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methyl-hydrazine
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Mn2+
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complete inhibition of nitrite synthesis at 0.1 mM; complete inhibition of the oxidation of HNO to NO at 0.001 mM, inhibition of HNO2 synthesis is the same at pH 6,7,8 and 9
Na2S
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50% inhibition at 0.3 mM
NaCl
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15 mM, 50% inhibition of activity with horse heart cytochrome, activity with pseudoazurin or cytochrome c550 is inhibited only above 100 mM
o-phenanthroline
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50% inhibition at 0.12 mM
phenazine methosulfate
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inhibitory above 0.1 mM
phenyl hydrazine
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N2H3 protects
additional information
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ACTIVATING COMPOUND
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
IMAGE
8-hydroxyquinoline
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1.5fold stimulation at 0.1 mM
cyanide
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2fold stimulation at 1 mM
diethyldithiocarbamate
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stimulation of nitrite production at 0.1 mM
KM VALUE [mM]
SUBSTRATE
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
IMAGE
0.017 - 0.2
cytochrome c
0.01
ferricytochrome c551
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pH 7.8, 25C
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0.07
horse heart ferricytochrome c
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in 10 mM Tris-HC1 (pH 8.0), at 30C
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0.003 - 0.005
hydrazine
0.35
hydroxylamine
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in 10 mM Tris-HC1 (pH 8.0), at 30C
0.033
pseudoazurin
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pH 7.8, 25C
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TURNOVER NUMBER [1/s]
SUBSTRATE
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
IMAGE
0.53 - 383
hydroxylamine
158
nitrite
Nitrosomonas europaea
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additional information
additional information
Nitrosomonas europaea
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overview: effect of pH on rate of reduction of heme c553 of the enzyme by NH2OH, rate constant for reduction of hemes of the enzyme by dithionite at 2C and 19C and by NH2OH or NH2NH2 at 2C
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IC50 VALUE [mM]
INHIBITOR
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
IMAGE
0.01
EDTA
Arthrobacter globiformis
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at pH 9.0 and 30C
SPECIFIC ACTIVITY [µmol/min/mg]
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
3.6
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in 10 mM Tris-HC1 (pH 8.0), at 30C
8.94
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supernatant obtained by centrifugation
11.63
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supernatant obtained by centrifugation
25.6
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supernatant obtained by centrifugation
additional information
pH OPTIMUM
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
8.5
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activity with horse heart cytochrome c
10
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activity with pseudoazurin
10.5
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rate of reduction of hemes c 553 of the enzyme increases with pH
11
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activity with cytochrome c550 continues to increase to pH 11
pH RANGE
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
7.3 - 11.5
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pH 7.3: about 35% of maximal activity, pH 11.5: about 50% of maximal activity activity with pseudoazurin
7.6 - 10
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pH 7.6: about 50% of maximal activity, pH 10.0: about 35% of maximal activity with horse heart cytochrome c
8 - 11
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activity with cytochrome c550 continues to increase to pH 11, activity at pH 8 is about 50% of the activity at pH 11
TEMPERATURE OPTIMUM
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
TEMPERATURE RANGE
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
additional information
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changes in enzyme conformation imposed by changes in solvent, temperature or pressure affect the rates of intramolecular electron transfer from the substrate site to c hemes
LOCALIZATION
ORGANISM
UNIPROT
COMMENTARY hide
GeneOntology No.
LITERATURE
SOURCE
MOLECULAR WEIGHT
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
38900
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gel filtration
140000
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SDS-PAGE
175000 - 180000
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SDS-PAGE, gel filtration
180000 - 200000
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SDS-PAGE
189000
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calculated from amino acid sequence
200000
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sedimentation velocity experiments
SUBUNITS
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
hexamer
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3 * 63000 + 3 * 11000, (alpha,beta)3 subunit structure, SDS-PAGE, 200000 MW enzyme forms a 63000 MW monomer after heme removal, hydroxylamine oxidoreductase probably consists of 3 molecules of monoheme c-type cytochrome with a MW of 11000 and 3 tightly complexed molecules of a catalytically active MW 63000 protein containing 6 c-type hemes and one P-460 heme, SDS-PAGE
homotrimer
oligomer
trimer
Crystallization/COMMENTARY
ORGANISM
UNIPROT
LITERATURE
microbatch-under-oil method, using 0.1 M potassium nitrate, 0.1 M MES pH 7.5 and 46% (v/v) PEG 400; using 0.1 M potassium nitrate, 0.1 M MES pH 7.5 and 46% (w/v) PEG 400
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pH STABILITY
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
10.5
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enzyme is permanently inactivated above pH 10.5
394319
TEMPERATURE STABILITY
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
70
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90% loss of activity after 1 min at 70C
additional information
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changes in enzyme conformation imposed by changes in solvent, temperature or pressure affect the rates of intramolecular electron transfer from the substrate site to c hemes
GENERAL STABILITY
ORGANISM
UNIPROT
LITERATURE
relative stable for 72 hours during ammonia starvation
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ORGANIC SOLVENT
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
additional information
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changes in enzyme conformation imposed by changes in solvent, temperature or pressure affect the rates of intramolecular electron transfer from the substrate site to c hemes
Purification/COMMENTARY
ORGANISM
UNIPROT
LITERATURE
ammonium sulfate precipitation, DEAE cellulose column chromatography, gel filtration
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ammonium sulfate precipitation, Sepharose CL-6B column chromatography, DEAE-Sephacel column chromatography, and Sephadex G-100 gel filtration; ammonium sulfate precipitation, Sepharose CL-6B column chromatography, DEAE-Sephacel gel filtration, and Sephadex G100 gel filtration
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Cloned/COMMENTARY
ORGANISM
UNIPROT
LITERATURE
cloned and expressed in Pseudomonas putida
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EXPRESSION
ORGANISM
UNIPROT
LITERATURE
in energy-depleted cells, hao 3 gene expression is increased in the presence of 30 mM NH4+
ENGINEERING
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
additional information