1.7.5.1: nitrate reductase (quinone)
This is an abbreviated version!
For detailed information about nitrate reductase (quinone), go to the full flat file.
Word Map on EC 1.7.5.1
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1.7.5.1
-
denitrification
-
denitrify
-
quinols
-
dissimilatory
-
chlorate
-
narj
-
narghji
-
molybdoenzyme
-
nitrate-reducing
-
menaquinol
-
nitrate-dependent
-
q-site
-
stigmatellin
-
menasemiquinone
-
hyscore
-
menadiol
- 1.7.5.1
-
denitrification
-
denitrify
- quinols
-
dissimilatory
- chlorate
- narj
-
narghji
-
molybdoenzyme
-
nitrate-reducing
- menaquinol
-
nitrate-dependent
-
q-site
- stigmatellin
-
menasemiquinone
-
hyscore
- menadiol
Reaction
Synonyms
EC 1.7.99.4, gene narH, membrane-bound nitrate reductase, membrane-bound quinol:nitrate oxidoreductase, MSMEG_5140, NaR, NaR1, NarG, NarGHI, narH, NarI, NarZ, nitrate reducatse A, nitrate reductase A, nitrate reductase Z, NRA nitrate reductase A, NRZ, NRZ nitrate reductase, Pden_4236, quinol-nitrate oxidoreductase, quinol/nitrate oxidoreductase, quinol:nitrate oxidoreductase, SCO6532, SCO6533, SCO6534, SCO6535
ECTree
1.7.5.1 nitrate reductase (quinone)Advanced search results
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results (Substrates Products
Substrates Products on EC 1.7.5.1 - nitrate reductase (quinone)
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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
nitrate + 2,3-dimethoxy-5-methyl-6-decyl-1,4-benzoquinol
nitrite + 2,3-dimethoxy-5-methyl-6-decyl-1,4-benzoquinone + H2O
-
i.e. decylubiquinol
-
-
?
nitrate + 2-hydroxy-3-(3-methyl-2-butenyl)-1,4-naphthoquinol
nitrite + 2-hydroxy-3-(3-methyl-2-butenyl)-1,4-naphthoquinone + H2O
nitrate + 5-hydroxy-2-methyl-1,4-naphthoquinol
nitrite + 5-hydroxy-2-methyl-1,4-naphthoquinone + H2O
-
-
-
-
?
nitrate + 5-hydroxy-2-methyl-naphthalene-1,4-diol
nitrite + 5-hydroxy-2-methyl-naphthalene-1,4-dione + H2O
nitrate + menaquinol
nitrite + menaquinone + H2O
-
only the membrane-bound, not the solubilized form of the enzyme, can accept electrons from a menaquinone analog, menadione, whereas both forms can accept electrons from methylviologen. In vivo quinol interacts directly with the gamma subunit that is lost during solubilization
-
-
?
nitrate + quinol
nitrite + quinone
-
NarGHI strongly stabilizes a semiquinone radical located within the dihemic anchor subunit NarI. The semiquinone is located within the quinol oxidation site QD
-
-
?
nitrite + menaquinone + H2O
nitrate + menaquinol
-
-
-
?
nitrite + naphthoquinone + H2O
nitrate + naphthoquinol
-
-
-
?
nitrate + 2-hydroxy-3-(3-methyl-2-butenyl)-1,4-naphthoquinol
nitrite + 2-hydroxy-3-(3-methyl-2-butenyl)-1,4-naphthoquinone + H2O
-
-
-
-
?
nitrate + 2-hydroxy-3-(3-methyl-2-butenyl)-1,4-naphthoquinol
nitrite + 2-hydroxy-3-(3-methyl-2-butenyl)-1,4-naphthoquinone + H2O
-
-
-
?
nitrate + 2-hydroxy-3-(3-methyl-2-butenyl)-1,4-naphthoquinol
nitrite + 2-hydroxy-3-(3-methyl-2-butenyl)-1,4-naphthoquinone + H2O
-
-
-
?
nitrate + 2-methyl-1,4-naphthoquinol
nitrite + 2-methyl-1,4-naphthoquinone + H2O
-
i.e menadiol
-
-
?
nitrate + 2-methyl-1,4-naphthoquinol
nitrite + 2-methyl-1,4-naphthoquinone + H2O
-
i.e. menadiol
-
-
?
nitrate + 2-methyl-1,4-naphthoquinol
nitrite + 2-methyl-1,4-naphthoquinone + H2O
i.e. menadiol
-
-
?
nitrate + 2-methyl-1,4-naphthoquinol
nitrite + 2-methyl-1,4-naphthoquinone + H2O
-
i.e. menadiol. As the reduction of nitrate to nitrite requires two electrons, there must necessarily be two successive bindings of quinone, with transfer of one electron to the hemes, then to the [Fe-S] cluster, to be finally accumulated at the level of the molybdenum cofactor to be able to undertake the catalytic reaction. There are two distinct reactions, depending on whether the hemes were previously reduced by menadiol or by duroquinol. A two-pathway electron transfer model for nitrate reductase A is proposed
-
-
?
nitrate + 2-methyl-1,4-naphthoquinol
nitrite + 2-methyl-1,4-naphthoquinone + H2O
-
i.e. menadiol. Electrons from menadiol oxidation are transferred initially to heme bL
-
-
?
nitrate + 5-hydroxy-1,4-naphthoquinol
nitrite + 5-hydroxy-1,4-naphthoquinone + H2O
-
i.e. juglone
-
-
?
nitrate + 5-hydroxy-1,4-naphthoquinol
nitrite + 5-hydroxy-1,4-naphthoquinone + H2O
-
i.e. reduced form of juglone
-
-
?
nitrate + 5-hydroxy-2-methyl-naphthalene-1,4-diol
nitrite + 5-hydroxy-2-methyl-naphthalene-1,4-dione + H2O
-
i.e plumbagin
-
-
?
nitrate + 5-hydroxy-2-methyl-naphthalene-1,4-diol
nitrite + 5-hydroxy-2-methyl-naphthalene-1,4-dione + H2O
-
i.e. reduced form of plumbagin
-
-
?
nitrate + 5-hydroxy-2-methyl-naphthalene-1,4-diol
nitrite + 5-hydroxy-2-methyl-naphthalene-1,4-dione + H2O
-
i.e. reduced form of plumbagin
i.e. plumbagin
-
?
nitrate + duroquinol
nitrite + duroquinone + H2O
-
if quinols are used as the electron donor the enzyme operates by a two-site, enzyme-substitution mechanism
-
-
?
nitrate + quinol
nitrite + quinone + H2O
-
first enzyme involved in respiratory denitrification in prokaryotes
-
-
?
nitrate + quinol
nitrite + quinone + H2O
-
in order to use nitrate as an electron acceptor, Escherichia coli synthesises three distinct enzymes: a membrane-bound enzyme (nitrate reductase A, NarGHI) encoded by the narGHJI operon and a soluble periplasmic nitrate reductase (NapAB, EC 1.9.6.1) encoded by the napFDAGHBC operon. A second membrane-bound nitrate reductase (nitrate reductase Z, NarZYV) encoded by the NarZYWV operon is biochemically similar to NarGHI. Whereas NarGHI synthesis is induced by nitrate under anaerobic conditions, NarZYV is expressed at a cryptic level and may assist Escherichia coli in transition from aerobic to anaerobic respiration (physiological role of this isoenzyme at the onset of the stationary growth phase in rich media). NapAB is mainly expressed in the presence of low concentrations of nitrate under both aerobic and anaerobic conditions, and its expression is suppressed at high nitrate concentrations. Conversely, NarGHI is maximally expressed when nitrate concentration is elevated, and under these conditions becomes the predominant enzyme in Escherichia coli. Thus, NapAB (Ec 1.9.6.1) and NarGHI seem to function in different ranges of nitrate concentration in a complementary way to support anaerobic respiration on nitrate under anaerobic conditions and in the presence of nitrate
-
-
?
nitrate + quinol
nitrite + quinone + H2O
model of electron transfer in the nitrate reductase: electrons are provided by quinones to the NarI subunit and subsequently transferred to NarH, which eventually delivers them to the molybdenum cofactor where nitrate reduction takes place
-
-
?
nitrate + quinol
nitrite + quinone + H2O
nitrate reductase A reduces nitrate to nitrite and forms part of a redox loop generating a proton-motive force
-
-
?
nitrate + quinol
nitrite + quinone + H2O
under anaerobic conditions in the presence of nitrate, Escherichia coli synthesizes the cytoplasmic membrane-bound quinol-nitrate oxidoreductase (nitrate reductase A, NarGHI), which reduces nitrate to nitrite and forms part of a redox loop generating a proton-motive force. The arrangement, coordination scheme and unique environment of the redox-active prosthetic groups is revealed
-
-
?
nitrate + quinol
nitrite + quinone + H2O
-
the enzyme is essential for the fungal denitrification. The fungal formate dehydrogenase can supply electrons via quinol/quinone pool to nitrate reductase A
-
-
?
nitrate + quinol
nitrite + quinone + H2O
-
the membrane-anchored protein directs electrons from quinol oxidation at the membrane anchor, NarI, to the site of nitrate reduction in the membrane extrinsic [Fe-S] cluster and Mo-bis-MGD containing dimer, NarGH
-
-
?
nitrate + reduced benzyl viologen
nitrite + benzyl viologen
-
-
-
?
nitrate + reduced benzyl viologen
nitrite + oxidized benzyl viologen + H2O
-
-
-
-
?
nitrate + reduced benzyl viologen
nitrite + oxidized benzyl viologen + H2O
-
-
-
?
nitrate + reduced benzyl viologen
nitrite + oxidized benzyl viologen + H2O
-
when reduced viologen dyes act as the electron donor, the enzyme follows a compulsory-order, Theorell-Chance mechanism, in which it is an enzyme-nitrate complex that is reduced rather than the free enzyme
-
-
?
nitrate + reduced methyl viologen
nitrite + oxidized methyl viologen + H2O
-
-
-
-
?
nitrate + reduced methyl viologen
nitrite + oxidized methyl viologen + H2O
-
when reduced viologen dyes act as the electron donor, the enzyme follows a compulsory-order, Theorell-Chance mechanism, in which it is an enzyme-nitrate complex that is reduced rather than the free enzyme
-
-
?
nitrate + reduced methyl viologen
nitrite + oxidized methyl viologen + H2O
-
catalysis under substrate-limiting conditions clearly occurs via two pathways with distinct kinetic properties reversibly linked by a redox event. This redox event may be integral to the catalytic cycle of the active site or occur at a center, remote from the description of active-site chemistry, which serves to switch NarGH between two catalytically competent forms
-
-
?
nitrate + reduced methyl viologen
nitrite + oxidized methyl viologen + H2O
-
-
-
-
?
nitrate + tetramethyl-p-benzoquinol
nitrite + tetramethyl-p-benzoquinone + H2O
-
i.e. duroquinol
-
-
?
nitrate + tetramethyl-p-benzoquinol
nitrite + tetramethyl-p-benzoquinone + H2O
i.e. duroquinol
-
-
?
nitrate + tetramethyl-p-benzoquinol
nitrite + tetramethyl-p-benzoquinone + H2O
-
i.e. duroquinol. As the reduction of nitrate to nitrite requires two electrons, there must necessarily be two successive bindings of quinone, with transfer of one electron to the hemes, then to the [Fe-S] cluster, to be finally accumulated at the level of the molybdenum cofactor to be able to undertake the catalytic reaction. There are two distinct reactions, depending on whether the hemes were previously reduced by menadiol or by duroquinol. A two-pathway electron transfer model for nitrate reductase A is proposed
-
-
?
nitrate + ubiquinol
nitrite + ubiquinone + H2O
-
-
-
?
nitrate + ubiquinol
nitrite + ubiquinone + H2O
-
if quinols are used as the electron donor the enzyme operates by a two-site, enzyme-substitution mechanism
-
-
?
nitrite + demethylmenaquinone + H2O
nitrate + demethylmenaquinol
-
-
-
?
nitrite + demethylmenaquinone + H2O
nitrate + demethylmenaquinol
endogeneous demethylmenasemiquinone (DMSK) intermediates are stabilized in the enzyme. DMSK is formed at the NarGHI QD quinol oxidation site
-
-
?
nitrite + ubiquinone + H2O
nitrate + ubiquinol
-
-
-
?
nitrite + ubiquinone + H2O
nitrate + ubiquinol
-
-
-
?
additional information
?
-
-
Escherichia coli expresses two different membrane-bound respiratory nitrate reductases, nitrate reductase A (NRA) and nitrate reductase Z (NRZ). The two enzymes are encoded by distinct operons located within two different loci on the Escherichia coli chromosome. The narGHJI operon, encoding nitrate reductase A, is located in the chlC locus at 27 min, along with several functionally related genes: narK, encoding a nitrate/nitrite antiporter, and the narXL operon, encoding a nitrate-activated, two component regulatory system. The narZYWV operon, encoding nitrate reductase Z, is located in the chlZ locus located at 32.5 min, a region which includes a narK homologue, narU, but no apparent homologue to the narXL operon. The two membrane-bound enzymes have similar structures and biochemical properties and are capable of reducing nitrate using normal physiological substrates. The homology of the amino acid sequences of the peptides encoded by the two operons is extremely high but the intergenic regions share no related sequences. The expression of both the narGHJI operon and the narK gene are positively regulated by two transacting factors Fnr and NarL-phosphate, activated respectively by anaerobiosis and nitrate, while the narZYWV operon and the narU gene are constitutively expressed. Nitrate reductase A, which accounts for 98% of the nitrate reductase activity when fully induced, is clearly the major respiratory nitrate reductase in Escherichia coli
-
-
?
additional information
?
-
-
nitrate reductase Z expression is regulated in a manner opposite to that of nitrate reductase A. The narGHJZ operon is aerobically repressed, strongly induced by nitrate and positively regulated by the fnr gene product. The expression of narZ is anaerobically repressed, induced weakly, if at all, by nitrate and negatively regulated by the fnr gene product. The opposing regulation of these two enzymes suggests that a function of nitrate reductase Z may be to catalyse the immediate flow of electrons to nitrate during an aerobic/anaerobic transition when the bacterium is grown in the presence of nitrate
-
-
?
additional information
?
-
-
NRZ is expressed at a low level that is not influenced by anaerobiosis or nitrate. The NRZ operon is controlled mainly at the level of transcription and is induced 10fold at the onset of stationary phase in rich media. Expression of NRZ nitrate reductase is highly growth phase dependent and is controlled by the alternative vegetative sigma factor RpoS. RpoS-mediated regulation of NRZ may be an important physiological adaptation that allows the cell to use nitrate under stress-associated conditions
-
-
?
additional information
?
-
-
bromate and chlorate are substrates of the enzyme
-
-
?
additional information
?
-
-
the holoenzyme has two independent and spatially distinct active sites, one for quinol oxidation and the other for nitrate reduction
-
-
?
additional information
?
-
structure-function relationships of quinone reactivity
-
-
?
additional information
?
-
structure-function relationships of quinone reactivity
-
-
?
additional information
?
-
structure-function relationships of quinone reactivity
-
-
?
additional information
?
-
-
structure-function relationships of quinone reactivity
-
-
?
additional information
?
-
-
nitrate reductase Z is synthesized in small amounts, the expression of its structural genes does not seem to be induced by nitrate, repressed by oxygen or activated by the product of the fnr gene. The nitrate reductase Z in mutant LCB79/pLCB14 couples formate oxidation with nitrate reduction probably via quinones and type-b cytochromes
-
-
?
additional information
?
-
-
nitrate reductase Z is able to use both nitrate and chlorate as substrate
-
-
?
