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Enzyme Nomenclature
Information on EC 1.13.12.16 - nitronate monooxygenase
for references in articles please use BRENDA:EC1.13.12.16
Word Map on EC 1.13.12.16
- 1.13.12.16
- nitroalkanes
- nitroethane
- hansenula
- mrakii
- neurospora
- crassa
- flavin
- fmn
-
denitrification
-
flavosemiquinone
- 1-nitropropane
-
enzyme-bound
-
3-nitropropionic
- saturnus
-
flavin-dependent
- semiquinone
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The expected taxonomic range for this enzyme is: Eukaryota, Bacteria
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EC NUMBER 
COMMENTARY 
1.13.12.16
-
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RECOMMENDED NAME
GeneOntology No.
nitronate monooxygenase
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REACTION
REACTION DIAGRAM
COMMENTARY
ORGANISM
UNIPROT
LITERATURE
ethylnitronate + O2 = acetaldehyde + nitrite + other products
ordered bi bi mechanism in which 2-nitropropane first combines with the enzyme and the enzyme 2-nitropropane complex reacts with oxygen to form a ternary complex; superoxide as reactive intermediate
-
ethylnitronate + O2 = acetaldehyde + nitrite + other products
superoxide as reactive intermediate
-
ethylnitronate + O2 = acetaldehyde + nitrite + other products
catalytic and kinetic reaction mechanism, comparison to the nitroalkane oxygenase, EC 1.7.3.1, and other flavin-dependent enzymes, ionization of nitroethane and ethylnitronate in aqueous solution, overview
-
ethylnitronate + O2 = acetaldehyde + nitrite + other products
catalytic and kinetic reaction mechanism, comparison to the nitroalkane oxigenase, EC 1.7.3.1, and other flavin-dependent enzymes, ionization of nitroethane and ethylnitronate in aqueous solution, overview. Enzymatic turnover begins with the rapid equilibrium association of ethylnitronate and the enzyme. In the oxidative pathway, the transfer of a single electron oxidizes the organic substrate and reduces the enzyme-bound flavin to an anionic semiquinone species, the electron transfer occurs while the substrate radical is still bound in the active site of the enzyme. After formation of the flavosemiquinone species in the active site of NMO, the subsequent oxidation of the one electron reduced flavin occurs when molecular oxygen reacts with the anionic flavosemiquinone to yield an enzyme-associated superoxide species, with second-order rate constants
-
ethylnitronate + O2 = acetaldehyde + nitrite + other products
catalytic and kinetic reaction mechanism, comparison to the nitroalkane oxygenase, EC 1.7.3.1, and other flavin-dependent enzymes, ionization of nitroethane and ethylnitronate in aqueous solution, overview
-
ethylnitronate + O2 = acetaldehyde + nitrite + other products
catalyze the oxidation of propionate-3-nitronate or other nitronate analogues through a radical mechanism involving a catalytic flavosemiquinone without formation of a canonical C4a-(hydro)peroxyflavin
-
ethylnitronate + O2 = acetaldehyde + nitrite + other products
ordered bi bi mechanism in which 2-nitropropane first combines with the enzyme and the enzyme 2-nitropropane complex reacts with oxygen to form a ternary complex; superoxide as reactive intermediate
-
-
ethylnitronate + O2 = acetaldehyde + nitrite + other products
catalytic and kinetic reaction mechanism, comparison to the nitroalkane oxygenase, EC 1.7.3.1, and other flavin-dependent enzymes, ionization of nitroethane and ethylnitronate in aqueous solution, overview
-
-
ethylnitronate + O2 = acetaldehyde + nitrite + other products
-
-
-
-
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REACTION TYPE
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
oxidation
-
-
-
-
redox reaction
-
-
-
-
reduction
-
-
-
-
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PATHWAY
BRENDA Link
KEGG Link
MetaCyc Link
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SYSTEMATIC NAME
IUBMB Comments
nitronate:oxygen 2-oxidoreductase (nitrite-forming)
Previously classified as 2-nitropropane dioxygenase (EC 1.13.11.32), but it is now recognized that this was the result of the slow ionization of nitroalkanes to their nitronate (anionic) forms. The enzymes from the fungus Neurospora crassa and the yeast Williopsis saturnus var. mrakii (formerly classified as Hansenula mrakii) contain non-covalently bound FMN as the cofactor. Neither hydrogen peroxide nor superoxide were detected during enzyme turnover. Active towards linear alkyl nitronates of lengths between 2 and 6 carbon atoms and, with lower activity, towards propyl-2-nitronate. The enzyme from N. crassa can also utilize neutral nitroalkanes, but with lower activity.
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CAS REGISTRY NUMBER
COMMENTARY
61584-55-2
-
65802-82-6
-
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ORGANISM
COMMENTARY
LITERATURE
UNIPROT
SEQUENCE DB
SOURCE
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GENERAL INFORMATION
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
evolution
-
NMO is a member of the group H flavin-dependent monooxygenases
malfunction
physiological function
additional information
-
four conserved motifs are identified in PA4202. Oxidation of propionate-3-nitronate by NMO yields malonic semialdehyde, which is an important metabolite that can be converted to acetyl-CoA, acetate, or 3-hydroxypropionate and enter various catabolic or anabolic pathways. Active site structure analysis, overview
malfunction
-
the mixture propionate-3-nitronate/3-nitropropionate is toxic to recombinant Escherichia coli cells lacking expression of NMO, but the toxicity is overcome through either induction of the gene for NMO or through addition of exogenous enzyme to the cultures
malfunction
-
a knockout mutant of Neurospora crassa lacking NMO is inhibited by concentrations of propionate-3-nitronate and 3-nitropropionate; the mixture propionate-3-nitronate/3-nitropropionate is toxic to recombinant Escherichia coli cells lacking expression of NMO, but the toxicity is overcome through either induction of the gene for NMO or through addition of exogenous enzyme to the cultures
malfunction
-
deletion of the nmoA gene results in an increased sensitivity of the cells to 3-nitropropionic acid (3-NPA), phenotype, overview
physiological function
-
role of the nitronate monooxygenase protein in the detoxification of nitronate. At physiological pH, 3-nitropropionate, a nitro toxin produced by plants and fungi, exists in equilibrium with its conjugate base, propionate-3-nitronate, the tauromer of 3-nitropropionic acid
physiological function
-
nitronate monooxygenase oxidizes the mitochondrial toxin propionate 3-nitronate to malonate semialdehyde, and detoxifies the deadly toxin
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SUBSTRATE
PRODUCT
REACTION DIAGRAM
ORGANISM
UNIPROT
COMMENTARY
(Substrate)
(Substrate)
LITERATURE
(Substrate)
(Substrate)
COMMENTARY
(Product)
(Product)
LITERATURE
(Product)
(Product)
Reversibility
r=reversible
ir=irreversible
?=not specified
r=reversible
ir=irreversible
?=not specified
1-hydroxybutyl-2-nitronate + O2
? + HNO2
-
anionic, expression on the basis of the reactivity of propyl-2-nitronate with 2-nitropropane dioxygenase: 31.5
-
-
?
2 Cu((CH3)2CNO2)(PPh3)2 + O2
2 Cu(O2N)(PPh3)2 + 2 propan-2-one
-
using a copper(I) aci-2-nitropropanate complex
-
-
?
2-hydroxybutyl-3-nitronate + O2
? + HNO2
-
anionic, expression on the basis of the reactivity of propyl-2-nitronate with 2-nitropropane dioxygenase: 26.7
-
-
?
2-hydroxypentyl-3-nitronate + O2
? + HNO2
-
anionic, expression on the basis of the reactivity of propyl-2-nitronate with 2-nitropropane dioxygenase: 32.3
-
-
?
2-nitro-1H-indene-1,3(2H)-dione + Cu(0) + N,N,N',N'-tetramethylethylenediamine + O2
1H-indene-1,2,3,-trione + (NO2)CuN,N,N',N'-tetramethylethylenediamine
-
with N,N-dimethylformamid (conversion: 30%) as solvent
-
-
?
2-nitroethanol + O2
glycoaldehyde + HNO2
-
13% of the activity with 2-nitropropane
-
-
?
2-nitroethanol + O2 + H2O
? + HNO2 + H2O2
-
8.4% relative activity (1-nitropropane: 100%)
-
-
?
2-nitropropane + O2 + H2O
acetone + HNO2 + H2O2
-
96.9% relative activity (1-nitropropane: 100%)
-
-
?
3-nitro-1-butanol + O2 + H2O
? + HNO2 + H2O2
-
15.7% relative activity (1-nitropropane: 100%)
-
-
?
3-nitro-2-butanol + O2 + H2O
? + HNO2 + H2O2
-
6.5% relative activity (1-nitropropane: 100%)
-
-
?
3-nitro-2-pentanol + O2 + H2O
2-hydroxy-pentane-3-one + HNO2 + H2O2
-
116% relative activity (1-nitropropane: 100%)
-
-
?
3-nitropropionate + O2 + H2O
? + HNO2 + H2O2
-
0.5% relative activity (1-nitropropane: 100%)
-
-
?
ethylnitronate + Cu(0) + N,N,N',N'-tetramethylethylenediamine + O2
acetone + (NO2)CuN,N,N',N'-tetramethylethylenediamine
-
with N,N-dimethylformamid (conversion: 60%) and pyridine (conversion: 90%) as solvent
-
-
?
nitrocyclohexane + O2 + H2O
cyclohexanone + HNO2 + H2O2
-
99.8% relative activity (1-nitropropane: 100%)
-
-
?
nitroethane + O2
acetaldehyde + HNO2 + 1,1-dinitroethane
-
in contrast with the unambiguous stoichiometry of 2-nitropropane oxidation, the nitroethane oxidation is stoichiometrically complicated; 1,1-dinitroethane and nitrate are formed as minor products
-
-
?
nitroethane + O2
ethylnitronate
-
2-nitropropane dioxygenase utilizes a branched catalytic mechanism with nitroethane as substrate. The branch point occurs at the enzyme-ethylnitronate complex and involves either the release of the nitronate or an oxidative denitrification reaction. The partitioning of the enzyme-nitronate complex results in the formation of multiple products from independent catalytic pathways with nitroethane as substrate for the enzyme. In the nonoxidative pathway, nitroethane is deprotonated by histidine 196 to generate ethylnitronate which is subsequently released from the enzyme as a reaction product. The oxidative denitrification pathway was established in previous studies of the enzyme and involves the oxidation of ethylnitronate by the enzyme bound flavin to generate acetaldehyde and nitrite as product
-
-
r
nitroethane + O2 + H2O
? + HNO2 + H2O2
-
51.8% relative activity (1-nitropropane: 100%)
-
-
?
nitromethane + O2 + H2O
? + HNO2 + H2O2
-
7.3% relative activity (1-nitropropane: 100%)
-
-
?
pentane-1-nitronate + Cu(0) + N,N,N',N'-tetramethylethylenediamine + O2
pentaldehyde + (NO2)CuN,N,N',N'-tetramethylethylenediamine
-
with N,N-dimethylformamid (conversion: 28%) and pyridine (conversion: 21%) as solvent
-
-
?
propyl-2-nitronate + Cu(0) + 1,10-phenanthroline + O2
propan-2-one + ?
-
with methanol (conversion: 42%), MeCN (conversion: 24%), and N,N-dimethylformamid (conversion: 43%)
-
-
?
propyl-2-nitronate + Cu(0) + 2,2'-bipyridine + O2
propan-2-one + ?
-
with methanol (conversion: 44%), MeCN (conversion: 54%), and N,N-dimethylformamid (conversion: 37%)
-
-
?
propyl-2-nitronate + Cu(0) + N,N,N',N'-tetramethylethylenediamine + O2
propan-2-one + (NO2)CuN,N,N',N'-tetramethylethylenediamine
-
with methanol (conversion: 70%), MeCN (conversion: 49%), N,N-dimethylformamid (conversion: 71%), and pyridine (conversion: 67%) as solvent
-
-
?
propyl-2-nitronate + Cu(0) + O2
propan-2-one + ?
-
without ligand and without solvent (conversion: 12%)
-
-
?
propylnitronate + O2
? + HNO2
-
anionic, expression on the basis of the reactivity of propyl-2-nitronate with 2-nitropropane dioxygenase: 57.9
-
-
?
undecan-6-nitronate + Cu(0) + N,N,N',N'-tetramethylethylenediamine + O2
undecan-6-one + (NO2)CuN,N,N',N'-tetramethylethylenediamine
-
with N,N-dimethylformamid (conversion: 66%) and pyridine (conversion: 67%) as solvent
-
-
?
1-nitrobutane + O2
butyraldehyde + HNO2
neutral and anionic form
-
-
?
1-nitrohexane + O2
hexanaldehyde + HNO2
neutral and anionic form
-
-
?
1-nitropentane + O2
? + HNO2
-
3% of the activity with 2-nitropropane
-
-
?
1-nitropentane + O2
pentanaldehyde + HNO2
neutral and anionic form
-
-
?
1-nitropropane + O2
propionaldehyde + HNO2
57.9% of activity with 2-nitropropane
-
-
?
1-nitropropane + O2
propionaldehyde + HNO2
-
23.4% of the activity with 2-nitropropane
-
-
?
1-nitropropane + O2
propionaldehyde + HNO2
57.9% of activity with 2-nitropropane (anionic form)
-
-
?
1-nitropropane + O2
propionaldehyde + HNO2
-
23.4% of the activity with 2-nitropropane
-
-
?
1-nitropropane + O2
propionaldehyde + HNO2
-
21% of the activity with 2-nitropropane
-
-
?
1-nitropropane + O2
propionaldehyde + HNO2
neutral and anionic form
-
-
?
2-nitro-1-butanol + O2
1-hydroxy-butane-2-one + HNO2
31.5% of the activity with 2-nitropropane
-
-
?
2-nitro-1-butanol + O2
1-hydroxy-butane-2-one + HNO2
2.7% of the activity with 2-nitropropane
-
-
?
2-nitro-1-butanol + O2
1-hydroxy-butane-2-one + HNO2
2.7% of the activity with 2-nitropropane (anionic form)
-
-
?
2-nitro-1-butanol + O2
1-hydroxy-butane-2-one + HNO2
31.5% of the activity with 2-nitropropane (anionic form)
-
-
?
2-nitro-1-propanol + O2
1-hydroxy-propane-2-one + HNO2
7.7% of activity with 2-nitropropane
-
-
?
2-nitro-1-propanol + O2
1-hydroxy-propane-2-one + HNO2
7.7% of activity with 2-nitropropane (anionic form)
-
-
?
2-nitropropane + O2
acetone + HNO2
-
superoxide as reactive intermediate
-
-
?
2-nitropropane + O2
acetone + HNO2
-
superoxide as reactive intermediate
-
-
?
3 propionate-3-nitronate + O2
3 malonic semialdehyde + nitrite + 2 nitrate + H2O2
-
-
-
?
3 propionate-3-nitronate + O2
3 malonic semialdehyde + nitrite + 2 nitrate + H2O2
-
-
-
-
?
3 propionate-3-nitronate + O2
3 malonic semialdehyde + nitrite + 2 nitrate + H2O2
-
best substrate
-
-
?
3-nitro-2-butanol + O2
3-hydroxy-butane-2-one + HNO2
26.7% of the activity with 2-nitropropane
-
-
?
3-nitro-2-butanol + O2
3-hydroxy-butane-2-one + HNO2
-
13% of the activity with 2-nitropropane
-
-
?
3-nitro-2-butanol + O2
3-hydroxy-butane-2-one + HNO2
-
slight oxidation
-
-
?
3-nitro-2-butanol + O2
3-hydroxy-butane-2-one + HNO2
26.7% of the activity with 2-nitropropane (anionic form)
-
-
?
3-nitro-2-butanol + O2
3-hydroxy-butane-2-one + HNO2
-
14% of the activity with 2-nitropropane
-
-
?
3-nitro-2-pentanol + O2
2-hydroxy-pentane-3-one + HNO2
32.3% of the activity with 2-nitropropane
-
-
?
3-nitro-2-pentanol + O2
2-hydroxy-pentane-3-one + HNO2
-
40.6% of the activity with 2-nitropropane
-
-
?
3-nitro-2-pentanol + O2
2-hydroxy-pentane-3-one + HNO2
32.3% of the activity with 2-nitropropane (anionic form)
-
-
?
3-nitro-2-pentanol + O2
2-hydroxy-pentane-3-one + HNO2
-
20% of the activity with 2-nitropropane
-
-
?
3-nitropropionic acid + O2
?
25.5% of the activity with 2-nitropropane
-
-
?
3-nitropropionic acid + O2
?
-
11.7% of the activity with 2-nitropropane
-
-
?
3-nitropropionic acid + O2
?
25.5% of the activity with 2-nitropropane (anionic form)
-
-
?
3-nitropropionic acid + O2
?
-
12% of the activity with 2-nitropropane
-
-
?
ethylnitronate + O2
acetaldehyde + HNO2
-
anionic, expression on the basis of the reactivity of propyl-2-nitronate with 2-nitropropane dioxygenase: 32.5
-
-
?
ethylnitronate + O2
acetaldehyde + HNO2
neutral and anionic form
-
-
?
ethylnitronate + O2 + FMNH2
acetaldehyde + nitrite + FMN + H2O
-
-
-
-
?
ethylnitronate + O2 + FMNH2
acetaldehyde + nitrite + FMN + H2O
-
-
-
-
?
ethylnitronate + O2 + FMNH2
acetaldehyde + nitrite + FMN + H2O
-
reaction via ethylnitronate radical. Catalytic turnover of NMO with ethylnitronate as substrate occurs through both an oxidative denitrification pathway and a non-oxidative pathway in which the anionic substrate is protonated in the active site of the enzyme to form nitroethane as a reaction product
-
-
?
ethylnitronate + O2 + FMNH2
acetaldehyde + nitrite + FMN + H2O
-
-
-
-
?
nitrocyclohexane + O2
? + HNO2
-
2% of the activity with 2-nitropropane
-
-
?
nitrocyclohexane + O2
cyclohexanone + HNO2
1.5% of the activity with 2-nitropropane
-
-
?
nitrocyclohexane + O2
cyclohexanone + HNO2
1.5% of the activity with 2-nitropropane (anionic form)
-
-
?
nitroethane + O2
acetaldehyde + HNO2
4.2% of the activity with 2-nitropropane
-
-
?
nitroethane + O2
acetaldehyde + HNO2
-
88% of the activity with nitroethane
-
?
nitroethane + O2
acetaldehyde + HNO2
-
formation of 1,1-dinitroethane and nitrate as minor products
-
-
?
nitroethane + O2
acetaldehyde + HNO2
4.2% of the activity with 2-nitropropane (anionic form)
-
-
?
nitroethane + O2
acetaldehyde + HNO2
-
88% of the activity with nitroethane
-
-
?
nitroethane + O2
acetaldehyde + HNO2
-
27% of the activity with 2-nitropropane
-
-
?
nitroethane + O2
acetaldehyde + HNO2
-
The kinetic isotope effect on the second-order rate constant for nitronate formation, kcat/Km, decreases from an upper limiting value of 23 at low pH to a lower limiting value of 11 at high pH. The difference in the kinetic isotope effects arises from the branching of an enzyme-ethylnitronate reaction intermediate through oxidative and nonoxidative turnover. This branching is isotope sensitive due to a kinetic isotope effect on nitronate release rather than on flavin reduction. The kinetic isotope effect on ethylnitronate release arises from the deprotonation of histidine 196, which provides electrostatic interactions with the nitronate to keep it bound in the active site for oxidation. The isotope effect on branching results in an inflation of the kinetic isotope observed for the nonoxidative pathway to values that are larger than the intrinsic values associated with C-H bond cleavage
-
-
?
nitroethane + O2
acetaldehyde + nitrite
-
2-nitropropane dioxygenase utilizes a branched catalytic mechanism with nitroethane as substrate. The branch point occurs at the enzyme-ethylnitronate complex and involves either the release of the nitronate or an oxidative denitrification reaction. The partitioning of the enzyme-nitronate complex results in the formation of multiple products from independent catalytic pathways with nitroethane as substrate for the enzyme. In the nonoxidative pathway, nitroethane is deprotonated by histidine 196 to generate ethylnitronate which is subsequently released from the enzyme as a reaction product. The oxidative denitrification pathway was established in previous studies of the enzyme and involves the oxidation of ethylnitronate by the enzyme bound flavin to generate acetaldehyde and nitrite as product
-
-
?
nitroethane + O2
acetaldehyde + nitrite
-
catalytic turnover of NMO with nitroethane as substrate occurs with oxidative and non-oxidative pathways with ethylnitronate formation and release in assays of the enzyme with the neutral substrate. The nonoxidative pathway of the enzyme with nitroethane as substrate also involves the H196-catalyzed deprotonation of the nitroalkane and the release of ethylnitronate as a reaction product
-
-
?
nitromethane + O2
formaldehyde + HNO2
4.2% of the activity with 2-nitropropane activity
-
-
?
nitromethane + O2
formaldehyde + HNO2
4.2% of the activity with 2-nitropropane activity (anionic form)
-
-
?
nitromethane + O2
formaldehyde + HNO2
-
is not a substrate, under anaerobic conditions. The aerobic dialysis of the enzyme treated with nitromethane causes reoxidation of only the Fe2+
-
-
?
propyl-2-nitronate + O2 + FMNH2
? + nitrite + FMN + H2O
-
-
-
-
?
additional information
?
-
-
anaerobic substrate reduction and kinetic data using a Clark oxygen electrode to measure rates of oxygen consumption indicated that the enzyme is active on a broad range of alkyl nitronates, with a marked preference for unbranched substrates over propyl-2-nitronate. The enzyme utilizes alkyl nitronates for catalysis, but not nitroalkanes
-
-
-
additional information
?
-
-
enzyme catalyzes the oxygenative denitrification of anionic nitroalkanes much more effectively than that of the neutral ones
-
-
-
additional information
?
-
enzyme catalyzes the oxygenative denitrification of anionic nitroalkanes much more effectively than that of the neutral ones
-
-
-
additional information
?
-
-
anaerobic substrate reduction and kinetic data using a Clark oxygen electrode to measure rates of oxygen consumption indicates that the enzyme is active on a broad range of alkyl nitronates, with a marked preference for unbranched substrates over propyl-2-nitronate. The enzyme utilizes alkyl nitronates for catalysis, but not nitroalkanes
-
-
-
additional information
?
-
-
no activity, nitromethane is inert to the enzyme. The nitroalkanes are not oxidized under anaerobic conditions
-
-
-
additional information
?
-
-
sodium dithionite also reduces both the enzyme-bound FAD and Fe3+ under anaerobic conditions
-
-
-
additional information
?
-
-
sodium dithionite also reduces both the enzyme-bound FAD and Fe3+ under anaerobic conditions
-
-
-
additional information
?
-
-
only alkyl nitronates are used as substrates in the oxidative denitrification reaction catalyzed by Williopsis saturnus var. mrakii NMO, nitroalkanes are no substrates. The different substrate specificity compared to other NMOs might result from the presence of a His residue in the active site and conformational differences. NMO does not produce and release hydrogen peroxide during turnover with linear alkyl nitronates of various lengths between 2 and 6 carbon atoms or with propyl-2-nitronate. With the exception of propyl-2-nitronate, there is no release of superoxide during turnover of NMO at pH 8.0 and 30°C with linear alkyl nitronates with chain lengths between 2 and 6 carbon atoms
-
-
-
additional information
?
-
-
only alkyl nitronates are used as substrates in the oxidative denitrification reaction catalyzed by Williopsis saturnus var. mrakii NMO, nitroalkanes are no substrates. The different substrate specificity compared to other NMOs might result from the presence of a His residue in the active site and conformational differences. NMO does not produce and release hydrogen peroxide during turnover with linear alkyl nitronates of various lengths between 2 and 6 carbon atoms or with propyl-2-nitronate. With the exception of propyl-2-nitronate, there is no release of superoxide during turnover of NMO at pH 8.0 and 30°C with linear alkyl nitronates with chain lengths between 2 and 6 carbon atoms
-
-
-
additional information
?
-
-
active on primary and secondary nitroalkanes, with a marked preference for unbranched primary nitroalkanes
-
-
-
additional information
?
-
-
anionic forms of nitroalkanes are much better substrates than are neutral forms, enzyme does not act on aromatic compounds
-
-
-
additional information
?
-
-
the reduced enzyme can reduce the substrate under anaerobically conditions, substrate specificity with nitroalkanes and alkyl nitronates, O2 is delivered from air-saturated buffer in the assay reaction, enzyme catalyzes the 2-step oxidative denitrification of nitroalkanes to their corresponding carbonyl compounds and nitrite
-
-
-
additional information
?
-
the reduced enzyme can reduce the substrate under anaerobically conditions, substrate specificity with nitroalkanes and alkyl nitronates, O2 is delivered from air-saturated buffer in the assay reaction, enzyme catalyzes the 2-step oxidative denitrification of nitroalkanes to their corresponding carbonyl compounds and nitrite
-
-
-
additional information
?
-
-
enzyme is more specific for nitronates than nitroalkanes
-
-
-
additional information
?
-
enzyme is more specific for nitronates than nitroalkanes
-
-
-
additional information
?
-
-
2-nitropropane dioxygenase utilizes a branched catalytic mechanism with nitroethane as substrate. The branch point occurs at the enzyme-ethylnitronate complex and involves either the release of the nitronate or an oxidative denitrification reaction. The partitioning of the enzyme-nitronate complex results in the formation of multiple products from independent catalytic pathways with nitroethane as substrate for the enzyme. In the nonoxidative pathway, nitroethane is deprotonated by histidine 196 to generate ethylnitronate which is subsequently released from the enzyme as a reaction product
-
-
-
additional information
?
-
-
anionic forms of nitroalkanes are much better substrates than are neutral forms, enzyme does not act on aromatic compounds. Measuring nitrite production with 20 mM anionic nitro compounds as substrates
-
-
-
additional information
?
-
-
both the neutral and anionic forms of nitroalkanes act as substrates for the oxidative denitrification reaction catalyzed by Neurospora crassa NMO. NMO does not produce and release hydrogen peroxide during turnover with linear alkyl nitronates of various lengths between 2 and 6 carbon atoms or with propyl-2-nitronate. With the exception of propyl-1- and propyl-2-nitronate, there is no release of superoxide during turnover of NMO at pH 8.0 and 30°C with linear alkyl nitronates with chain lengths between 2 and 6 carbon atoms
-
-
-
additional information
?
-
-
the enzyme is active on propionate-3-nitronate and other alkyl nitronates, but cannot oxidize nitroalkanes, e.g. 3-nitropropionate, nitroethane, 1-nitropropane, 1-nitrobutane, 1-nitropentane, or 2-nitropropane. Anaerobic reduction of the enzyme with propionate-3-nitronate yields a flavosemiquinone
-
-
-
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NATURAL SUBSTRATES
NATURAL PRODUCTS
REACTION DIAGRAM
ORGANISM
UNIPROT
COMMENTARY
(Substrate)
(Substrate)
LITERATURE
(Substrate)
(Substrate)
COMMENTARY
(Product)
(Product)
LITERATURE
(Product)
(Product)
REVERSIBILITY
r=reversible
ir=irreversible
?=not specified
r=reversible
ir=irreversible
?=not specified
3 propionate-3-nitronate + O2
3 malonic semialdehyde + nitrite + 2 nitrate + H2O2
Q9HWH9
-
-
-
?
3 propionate-3-nitronate + O2
3 malonic semialdehyde + nitrite + 2 nitrate + H2O2
-
-
-
-
?
ethylnitronate + O2 + FMNH2
acetaldehyde + nitrite + FMN + H2O
-
-
-
-
?
ethylnitronate + O2 + FMNH2
acetaldehyde + nitrite + FMN + H2O
-
-
-
-
?
ethylnitronate + O2 + FMNH2
acetaldehyde + nitrite + FMN + H2O
-
-
-
-
?
propyl-2-nitronate + O2 + FMNH2
? + nitrite + FMN + H2O
-
-
-
-
?
additional information
?
-
-
enzyme catalyzes the oxygenative denitrification of anionic nitroalkanes much more effectively than that of the neutral ones
-
-
-
additional information
?
-
Q12723
enzyme catalyzes the oxygenative denitrification of anionic nitroalkanes much more effectively than that of the neutral ones
-
-
-
additional information
?
-
-
only alkyl nitronates are used as substrates in the oxidative denitrification reaction catalyzed by Williopsis saturnus var. mrakii NMO, nitroalkanes are no substrates. The different substrate specificity compared to other NMOs might result from the presence of a His residue in the active site and conformational differences. NMO does not produce and release hydrogen peroxide during turnover with linear alkyl nitronates of various lengths between 2 and 6 carbon atoms or with propyl-2-nitronate. With the exception of propyl-2-nitronate, there is no release of superoxide during turnover of NMO at pH 8.0 and 30°C with linear alkyl nitronates with chain lengths between 2 and 6 carbon atoms
-
-
-
additional information
?
-
-
only alkyl nitronates are used as substrates in the oxidative denitrification reaction catalyzed by Williopsis saturnus var. mrakii NMO, nitroalkanes are no substrates. The different substrate specificity compared to other NMOs might result from the presence of a His residue in the active site and conformational differences. NMO does not produce and release hydrogen peroxide during turnover with linear alkyl nitronates of various lengths between 2 and 6 carbon atoms or with propyl-2-nitronate. With the exception of propyl-2-nitronate, there is no release of superoxide during turnover of NMO at pH 8.0 and 30°C with linear alkyl nitronates with chain lengths between 2 and 6 carbon atoms
-
-
-
additional information
?
-
-
active on primary and secondary nitroalkanes, with a marked preference for unbranched primary nitroalkanes
-
-
-
additional information
?
-
-
enzyme is more specific for nitronates than nitroalkanes
-
-
-
additional information
?
-
Q01284
enzyme is more specific for nitronates than nitroalkanes
-
-
-
additional information
?
-
-
both the neutral and anionic forms of nitroalkanes act as substrates for the oxidative denitrification reaction catalyzed by Neurospora crassa NMO. NMO does not produce and release hydrogen peroxide during turnover with linear alkyl nitronates of various lengths between 2 and 6 carbon atoms or with propyl-2-nitronate. With the exception of propyl-1- and propyl-2-nitronate, there is no release of superoxide during turnover of NMO at pH 8.0 and 30°C with linear alkyl nitronates with chain lengths between 2 and 6 carbon atoms
-
-
-
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COFACTOR
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
IMAGE
cytochrome c
-
cytochrome c also inhibits the reaction and half-inhibition is found in the presence of 17 microM cytochrome c. The addition of cytochrome c to the reaction mixture containing 2-nitropropane and 2-nitropropane dioxygenase causes an increase in absorbance at 550 nm indicating the reduction of cytochrome c
FAD
-
contains 1 mol FAD per mol of enzyme; contains 1 mol FAD per mol of enzynme
FAD
-
contains 0.95 mol of FAD per mol of enzyme; contains 0.95 mol of FAD per mol of enzyme. The enzyme-bound FAD is reduced by 2-nitropropane under anaerobic conditions
FMN
-
2 mol of FMN per mol of subunit; dependent, enzyme contains flavin mononucleotide as a prosthetic group, 2 mol of FMN per mol of subunit
FMN
contains a mol of non-covalently bound FMN per mol of subunit, contains 0.84 FMN per monomer of enzyme; dependent on, stoichiometry of 0.84 FMN per 1 monomer of enzyme, noncovalently bound; dependent on, stoichiometry of 0.84 FMN per 1 monomer of enzyme, noncovalently bound, contains a mol of non-covalently bound FMN per mol of subunit, contains 0.84 FMN per monomer of enzyme
FMN
-
present in a 1:1 stoichiometry with the protein. The tight binding of sulfite (Kd = 0.09 mM, at pH 8 and 15°C) to the enzyme and the formation of the anionic flavosemiquinone upon anaerobic incubation with alkyl nitronates are consistent with the presence of a positively charged group in proximity of the N(1)-C(2)=O atoms of the FMN cofactor
FMN
-
contains a tightly, but not covalently, bound flavin that is required for enzymatic activity
FMN
-
contains a tightly, but not covalently, bound flavin that is required for enzymatic activity
FMN
-
contains a tightly, but not covalently, bound flavin that is required for enzymatic activity
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METALS and IONS
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
Fe
-
enzyme contains 1.09 gatom of iron per mol of enzyme; enzyme contains 1.09 gatom of iron per mol of enzyme
additional information
additional information
-
the enzyme contains negligible amounts of iron, manganese, zinc, and copper ions, which are not catalytically relevant
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INHIBITORS
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
IMAGE
acetone
-
inhibits competitively against 2-nitropropane, no inhibitory effect against O2
NADPH
-
competitive inhibitor. oxygenation is inhibited approximately 100% by 0.1 mM NADPH, respectively, although NAD+ and NADP+ are ineffective even at 1 mM. During the inhibition, NADH and NADPH are oxidized
nitrite
-
inhibits noncompetitively against 2-nitropropane, functioned as a noncompetitive inhibitor against oxygen in the presence of excess 2-nitropropane (50 mM)
NADH
-
competitive inhibitor. Oxygenation is inhibited approximately 86% by 0.1 mM NADH, although NAD+ and NADP+ are ineffective even at 1 mM. During the inhibition, NADH and NADPH are oxidized
Superoxide dismutase
-
; Cu and Zn-superoxide dismutase of bovine blood, Mn-superoxide dismutases of bacilli, Fe-superoxide dismutase of Serratia marcescens
-
Tiron
-
i.e. pyrocatechol-3,5-disulfonate disodium salt; i.e. pyrocatechol-3,5-disulfonate disodium salt, strong inhibition
additional information
-
EDTA does not inhibit the enzyme significantly. Iodoacetate is almost ineffective
-
additional information
-
inhibition by superoxide dismutase and various scavengers for superoxide; phenol, tryptophan, and tryptamine show no effect on the reaction
-
additional information
-
not affected by hydroxyl radical scavengers such as mannitol
-
additional information
-
superoxide dismutase and catalase have no effect on the enzymatic activity
-
additional information
-
no inhibition: tiron, superoxide dismutase, EDTA, cysteine, epinephrine, NADH, NADPH, and 2-mercaptoethanol
-
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ACTIVATING COMPOUND
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
IMAGE
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KM VALUE [mM]
SUBSTRATE
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
IMAGE
3.23
1-Nitropropane
-
anionic form of substrate; anionic form of the substrate
25.6
1-Nitropropane
-
neutral form of substrate; neutral form of the substrate
1.61
2-Nitropropane
-
anionic form of substrate; anionic form of the substrate
21.3
2-Nitropropane
-
neutral form of substrate; neutral form of the substrate
0.59
3-Nitro-2-butanol
-
anionic form of substrate; anionic form of the substrate
1.04
3-Nitro-2-pentanol
-
anionic form of substrate; anionic form of the substrate
3.13
nitroethane
-
anionic form of substrate; anionic form of the substrate
6.8
nitroethane
-
neutral form of substrate; neutral form of the substrate
24.3
nitroethane
-
neutral form of substrate; neutral form of the substrate
0.005
O2
-
with ethyl nitronate at pH 8.0 and 30°C; with ethyl nitronate at pH 8.0 and 30°C; with nitroethane at pH 9.0 and 30°C; with nitroethane at pH 9.0 and 30°C
0.034
O2
-
30°C, pH 8, mutant enzyme H196N; 30°C, pH 8, mutant enzyme H196N, ethylnitronate as a substrate
additional information
additional information
kinetics, steady-state kinetic mechanism
-
additional information
additional information
-
Km-value for O2 (wild-type enzyme) is below 0.005 mM
-
additional information
additional information
-
steady-state kinetic mechanism with ethylnitronate, overview
-
additional information
additional information
-
steady-state kinetic mechanism
-
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TURNOVER NUMBER [1/s]
SUBSTRATE
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
IMAGE
additional information
additional information
kcat at different conditions, overview, effects of presence of superoxide dimutase or catalase on the turnover rate of the enzyme
-
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kcat/KM VALUE [1/mMs-1]
SUBSTRATE
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
IMAGE
additional information
additional information
-
investigation of the pH effects on the kcat/Km-values
-
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Ki VALUE [mM]
INHIBITOR
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
IMAGE
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SPECIFIC ACTIVITY [µmol/min/mg]
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
80
after DEAE-Sepharose column chromatography and octyl-Sepharose column chromatography purification; after DEAE-Sepharose column chromatography and octyl-Sepharose column chromatography purification; at 25°C assay temperature, purified recombinant enzyme, substrate ethyl nitronate; at 25°C assay temperature, purified recombinant enzyme, substrate ethyl nitronate
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pH OPTIMUM
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
6.5
7.4
additional information
-
when the enzyme is dialyzed against 10 mM potassium phosphate buffer (pH 7.0) immediately after reduction by dithionite, the absorption spectrum similar to that of the native enzyme appears with concomitant restoration of approximately 80% of the activity
6.5
-
oxidation of anionic form of 2-nitropropane; oxidation of anionic form of 2-nitropropane
7
-
assay at, pH 8.0 for 2-nitropropane and 1-nitropropane and pH 7.0 for nitroethane
8
-
oxidation of neutral form of 2-nitropropane; oxidation of neutral form of 2-nitropropane
8
-
assay at, pH 8.0 for 2-nitropropane and 1-nitropropane and pH 7.0 for nitroethane
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pH RANGE
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
7 - 8.5
-
; when the enzyme is acidified to pH 3.0 and treated in the same way, the prosthetic groups do not dissociate from the protein and almost full activity remained
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TEMPERATURE OPTIMUM
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
30
37
40
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TEMPERATURE RANGE
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
20 - 45
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SOURCE TISSUE
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
SOURCE
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PDB
SCOP
CATH
ORGANISM
UNIPROT
Pseudomonas aeruginosa (strain ATCC 15692 / DSM 22644 / CIP 104116 / JCM 14847 / LMG 12228 / 1C / PRS 101 / PAO1)
Pseudomonas aeruginosa (strain ATCC 15692 / DSM 22644 / CIP 104116 / JCM 14847 / LMG 12228 / 1C / PRS 101 / PAO1)
Pseudomonas aeruginosa (strain ATCC 15692 / DSM 22644 / CIP 104116 / JCM 14847 / LMG 12228 / 1C / PRS 101 / PAO1)
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MOLECULAR WEIGHT
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
39920
calculated; calculated from the amino acid composition of the enzyme
40000
42000
42000
-
sedimentation equilibrium centrifugation; sedimentation equilibrium centrifugation
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SUBUNITS
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
dimer
homodimer
2 * 40000, gel filtration, heat denaturation, and mass spectroscopic analysis
monomer
additional information
monomer
-
1 * 37000, dynamic light scattering analysis; monomer1 * 37000, dynamic light scattering analysis
additional information
-
purified enzyme shows a single protein band upon disc-gel electrophoresis
additional information
-
enzyme surface structure analysis using the structure PDB Code 2GJN
additional information
-
the dimer interface includes eight contacts mainly in the FMN-binding domain and it does not seem to be directly relevant for catalysis as it is far from the active site pocket, structure analysis, overview
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Crystallization/COMMENTARY
ORGANISM
UNIPROT
LITERATURE
hanging drop vapour diffusion method using 10% (w/v) polyethylene glycol monomethyl ether 5000
-
purified recombinant His-tagged enzyme, vapor diffusion hanging drop method at room temperature, 0.002 ml of 14 mg/ml protein in 50 mM Tris-Cl, pH 8.0, 100 mM NaCl, 20 mM 2-nitropropane, with 0.002 ml of reservoir solution containing 14% w/v PEG 5000 monomethylether and 0.1 M Na-HEPES, pH 7.0, and equilibration against 1 ml of reservoir solution, 7-10 days, X-ray diffraction structure determination and analysis at 1.44 A resolution, molecular replacement
-
crystal structure of NAO from Streptomyces ansochromogenes is determined. It consists of two domains, a TIM barrel domain bound to FMN and C-terminal domain with a novel folding pattern
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pH STABILITY
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
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TEMPERATURE STABILITY
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
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GENERAL STABILITY
ORGANISM
UNIPROT
LITERATURE
gradual and irreversible loss of activity after treatment with 1% sodium lauryl sulfate or 6 M guanidine HCl, activity is reduced to 50% of its initial activity after 50 min at 37°C, complete loss of activity after 10 h
-
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STORAGE STABILITY
ORGANISM
UNIPROT
LITERATURE
-20°C, 1 mM or 10 mM potassium phosphate buffer, pH 7.0, at least 3 months
-
-20°C, 50 mM potassium phosphate, pH 7.4, 6 months, no loss of activity
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Purification/COMMENTARY
ORGANISM
UNIPROT
LITERATURE
; to homogeneity
DEAE fast flow column chromatography and Hi-Prep 16/10 octyl fast flow column chromatography; DEAE fast flow column chromatography and Hi-Prep 16/10 octyl fast flow column chromatography; recombinant enzyme from Escherichia coli strain BL21(DE3) by ammonium sulfate fractionation, DEAE and octyl resin chromatography; recombinant enzyme from Escherichia coli strain BL21(DE3) by ammonium sulfate fractionation, DEAE and octyl resin chromatography
HiLoad XK 16 Superdex 200 prep-grade column gel filtration and Mono Q HR5/5 column chromatography
-
recombinant His-tagged enzyme from Escherichia coli strain Rosetta(DE3)pLysS by affinity chromatography
-
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Cloned/COMMENTARY
ORGANISM
UNIPROT
LITERATURE
expressed in Escherichia coli
expressed in Escherichia coli BL21(DE3) cells; gene ncd-2, expression in Escherichia coli strain BL21(DE3), subcloning in strain XL-1 Blue; gene ncd-2, expression in Escherichia coli strain BL21(DE3), subcloning in strain XL-1 Blue; expressed in Escherichia coli BL21(DE3) cells
gene PA4202 or nmoA, monocistronic, low expression level gene, has an intergenic region of 97 nucleotides with neighbouring gene PA4201 (ddlA) encoding D-alanine alanine ligase, and an intergenic region of 107 nucleotides with gene PA4203 encoding a LysR regulator, PA4203 (nmoR) represses its own transcription and the expression of PA4202 (nmoA), presence of a single NmoR binding site between nmoA and nmoR, and interaction of NmoR with the intergenic nmoA-nmoR control region. In silico analysis of the ddlA-nmoA-nmoR-ppgL locus in Pseudomonas aeruginosa genomes, transcriptome analysis
-
gene pa4202, DNA and amino acid sequence determination and analysis, recombinant expression of His-tagged enzyme in Escherichia coli strain Rosetta(DE3)pLysS
-
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EXPRESSION
ORGANISM
UNIPROT
LITERATURE
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ENGINEERING
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
H196N
-
site-directed mutagenesis, does to catalyze the formation of ethylnitronate from nitroethane. It is a better catalyst than the wild-type enzyme for oxidative turnover with ethylnitronate; the H196N variant form of the enzyme does to catalyze the formation of ethylnitronate from nitroethane. The H196N variant is a better catalyst than the wild-type enzyme for oxidative turnover with ethylnitronate
H152A
-
His152 likely functions as the catalytic base that initiates oxidation of neutral substrates by abstracting a proton from the alpha-carbon; site-directed mutagenesis. His152 likely functions as the catalytic base that initiates oxidation of neutral substrates by abstracting a proton from the alpha-carbon
S288A
-
mutant enzyme forms inclusion bodies when overexpressed in Escherichia coli; site-directed mutagenesis. Mutant enzyme forms inclusion bodies when overexpressed in Escherichia coli
H179D
mutant enzyme shows no activity. Crystal structure of mutant H179D is determined: The structural superimposition of wild-type Sa-NAO and mutant H179D-nitroethane shows no significant structural variation
additional information
-
construction of an enzyme deletion mutant by the in vivo recombination system of the yeast Saccharomyces cerevisiae strain InvSc1, overview. Quantitative RT-PCR enzyme expression analysis. The expression of ddlA is not changed in the DELTAnmoA mutant compared to the wild-type
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LINKS TO OTHER DATABASES (specific for EC-Number 1.13.12.16)
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