Any feedback?
Information on EC 1.7.5.1 - nitrate reductase (quinone)
for references in articles please use BRENDA:EC1.7.5.1Please wait a moment until all data is loaded. This message will disappear when all data is loaded.
EC Tree
1.7.5.1 nitrate reductase (quinone)IUBMB Comments
A membrane-bound enzyme which supports anaerobic respiration on nitrate under anaerobic conditions and in the presence of nitrate. Contains the bicyclic form of the molybdo-bis(molybdopterin guanine dinucleotide) cofactor, iron-sulfur clusters and heme b. Escherichia coli expresses two forms NarA and NarZ, both being comprised of three subunits.
Specify your search results
Word Map
- 1.7.5.1
-
denitrification
-
denitrify
- quinols
-
dissimilatory
- chlorate
- narj
-
narghji
-
molybdoenzyme
-
nitrate-reducing
- menaquinol
-
nitrate-dependent
-
q-site
- stigmatellin
-
menasemiquinone
-
hyscore
- menadiol
The expected taxonomic range for this enzyme is: Bacteria, Archaea, Eukaryota
Synonyms
membrane-bound nitrate reductase, narghi, nitrate reductase a, nitrate reductase z, quinol-nitrate oxidoreductase, quinol/nitrate oxidoreductase, quinol:nitrate oxidoreductase, 
more
topPlease wait a moment until the data is sorted. This message will disappear when the data is sorted.
SYNONYM 
ORGANISM
UNIPROT
COMMENTARY 
LITERATURE
EC 1.7.99.4
-
-
formerly, part transferred
-
MSMEG_5140
NaR1
NarG
NarGHI
nitrate reducatse A
nitrate reductase A
nitrate reductase Z
Pden_4236
quinol:nitrate oxidoreductase
SCO6532
SCO6533
SCO6534
SCO6535
NarGHI
-
-
nitrate reductase A
-
-
Please wait a moment until the data is sorted. This message will disappear when the data is sorted.
REACTION
REACTION DIAGRAM
COMMENTARY
ORGANISM
UNIPROT
LITERATURE
nitrate + a quinol = nitrite + a quinone + H2O
-
-
-
-
nitrate + a quinol = nitrite + a quinone + H2O
electrons flow in the overall thermodynamically downhill direction from menaquinol (MQ) or ubiquinol (UQ) through the two hemes of NarI, the four [Fe-S] clusters of NarH, and then through the single [4Fe-4S] cluster of NarG to the Mo-bisPGD cofactor, where nitrate is reduced to nitrite
Please wait a moment until the data is sorted. This message will disappear when the data is sorted.
PATHWAY SOURCE
PATHWAYS
Please wait a moment until the data is sorted. This message will disappear when the data is sorted.
SYSTEMATIC NAME
IUBMB Comments
nitrite:quinone oxidoreductase
A membrane-bound enzyme which supports anaerobic respiration on nitrate under anaerobic conditions and in the presence of nitrate. Contains the bicyclic form of the molybdo-bis(molybdopterin guanine dinucleotide) cofactor, iron-sulfur clusters and heme b. Escherichia coli expresses two forms NarA and NarZ, both being comprised of three subunits.
Please wait a moment until the data is sorted. This message will disappear when the data is sorted.
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
-
-
?
Please wait a moment until the data is sorted. This message will disappear when the data is sorted.
NATURAL SUBSTRATE
NATURAL 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
nitrite + demethylmenaquinone + H2O
nitrate + demethylmenaquinol
-
-
-
?
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
-
-
?
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
?
-
-
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
-
-
?
Please wait a moment until the data is sorted. This message will disappear when the data is sorted.
COFACTOR
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
IMAGE
cytochrome bD
-
NarI is strongly associated with heme bD, Lys86 is required for its stabilization
-
cytochrome bH
-
both heme bL and heme bH are crucial components in the electron-transfer pathway from the subunit NarI through subunit NarH to the catalytic subunit NarG. Without heme bL electrons cannot be transferred from menaquinol to heme bH. On the other hand, in the absence of heme bH, electrons cannot be transferred from the reduced heme bL to the catalytic dimer NarGH. A complex of menadione radical anion associated with the enzyme, is formed during the process of heme reduction by menadiol
-
cytochrome bL
-
both heme bL and heme bH are crucial components in the electron-transfer pathway from the subunit NarI through subunit NarH to the catalytic subunit NarG. Without heme bL electrons cannot be transferred from menaquinol to heme bH. On the other hand, in the absence of heme bH, electrons cannot be transferred from the reduced heme bL to the catalytic dimer NarGH. A complex of menadione radical anion associated with the enzyme, is formed during the process of heme reduction by menadiol
-
demethylmenaquinone
DMKH2, endogeneous demethylmenasemiquinone (DMSK) intermediates are stabilized in the enzyme
heme b
-
the anchor subunit NarI contains two b-type hemes. Electron transfer out of NarI is mediated by two hemes, one of relatively low midpoint potential Em (heme bL), and one of relatively high Em (heme bH)
quinone
heme bD is distal to NarGH and constitutes part of the quinone binding and oxidation site (Q-site) through the axially coordinating His66 residue and one of the heme bD propionate groups. Bound quinone participates in hydrogen bonds with both the imidazole of His66 and the heme propionate
[4Fe-4S]-center
a single tetranuclear iron-sulfur [4Fe-4S] cluster, known as FS0, is bound to subunit NarG. NarH contains three [4Fe-4S] clusters (FS1-FS3) and one trinuclear iron-sulfur cluster ([3Fe-4S], FS4)
bis(molybdopterin guanine dinucleotide)molybdenum cofactor
-
evidence for the presence of interactions between the molybdenum cofactor (Moco) biosynthetic machinery and aponitrate reductase A. The final stages of molybdenum cofactor biosynthesis occurs on a complex made up by MogA, MoeA, MobA, and MobB, which is also in charge with the delivery of the mature cofactor onto the aponitrate reductase A in a NarJ-assisted process
bis(molybdopterin guanine dinucleotide)molybdenum cofactor
structural evidence for the role of an open bicyclic form of the molybdo-bis(molybdopterin guanine dinucleotide) cofactor in the catalytic mechanism
bis(molybdopterin guanine dinucleotide)molybdenum cofactor
-
the enzyme possesses a molybdopterin guanine dinucleotide active center. Two forms of the molybdenum center, high- and low-pH, are detectable by electron paramagnetic resonance spectroscopy
bis(molybdopterin guanine dinucleotide)molybdenum cofactor
the enzyme uses a molybdo-bis(molybdopterin guanine dinucleotide) cofactor for catalytic mechanism
bis(molybdopterin guanine dinucleotide)molybdenum cofactor
-
the molybdo-bis(molybdopterin guanine dinucleotide)-binding subunit NarG is organized in four domains around the molybdo-bis(molybdopterin guanine dinucleotide) cofactor
cytochrome
-
although the spectral studies of nitrate reductase Z reveals the presence of a b-type cytochrome subunit (1.5 mol/molecule of 230000 Da), none can be detected in the SDS-PAGE
-
cytochrome
-
NarI is strongly associated with heme bD, Lys86 is required for its stabilization
-
cytochrome
-
the spectrophotometric studies indicate that reduction of the cytochrome hemes varies according to the analogue of quinone used, and in no cases is it complete
-
cytochrome b
-
partial proteolysis of the cytochrome b containing holoenzyme by trypsin results in loss of cytochrome b and in cleavage of one of the subunits of the enzyme. The cytochrome-free derivative exhibits a viologen dye dependent activity that is indistinguishable from that of the holoenzyme, but it is incapable of catalyzing the quinol-dependent reaction
-
cytochrome b
-
the enzyme contains two b-type hemes in the gamma subunit. The two b-type centres are functional parts of the enzyme
-
cytochrome c
-
NarC contains a periplasmic cytochrome c, which is required for membrane attachment and maturation of the NarG catalytic subunit of the enzyme
cytochrome c
-
the isolated preparation contains heme c in a sub-stoichiometric amount with the ability to relay electrons to the molybdenum center, suggesting that this nitrate reductase may contain heme c instead of the heme b usually found in this class of enzymes
heme
-
the reduction of NarGHI hemes by menaquinol, the reduction exhibits four phases, a transient species associated with the enzyme is kinetically correlated to the second reduction of the hemes
heme
-
the spectrophotometric studies indicate that reduction of the cytochrome hemes varies according to the analogue of quinone used, and in no cases is it complete
heme
the transmembrane subunit NarI coordinates two low-spin hemes, heme bP and heme bD, which mediate electron transfer from the Q-site to the [Fe-S] clusters in NarH
heme
the membrane subunit (NarI) of Escherichia coli nitrate reductase A (NarGHI) contains two b-type hemes, both of which are the highly anisotropic low-spin type. Heme bD is distal to NarGH and constitutes part of the quinone binding and oxidation site (Q-site) through the axially coordinating His66 residue and one of the heme bD propionate groups. Bound quinone participates in hydrogen bonds with both the imidazole of His66 and the heme propionate
molybdenum bis-molybdopterin guanine dinucleotide
the enzyme binds one molybdenum-bis(molybdopterin guanine dinucleotide), i.e. Mo-bis-MGD, cofactor per subunit
molybdenum bis-molybdopterin guanine dinucleotide
the enzyme binds one molybdenum-bis(molybdopterin guanine dinucleotide), i.e. Mo-bis-MGD, cofactor per subunit
molybdenum bis-molybdopterin guanine dinucleotide
the enzyme binds one molybdenum-bis(molybdopterin guanine dinucleotide), i.e. Mo-bis-MGD, cofactor per subunit
molybdo-bis(pyranopterin guanine dinucleotide)
Mo-bisPGD cofactor, bound to subunit NarG. NarI anchors the NarGH subunits to the inside of the cytoplasmic membrane and contains two hemes b that are proximal (bP) and distal (bD) to the NarGH subunits, respectively
[4Fe-4S] cluster
the enzyme binds one [4Fe-4S] cluster per subunit
[4Fe-4S] cluster
the enzyme binds one [4Fe-4S] cluster per subunit
additional information
-
molecular characterization of a quinol binding and oxidation site (Q-site) in NarGHI
-
additional information
-
the semiquinone is located within the quinol oxidation site QD
-
additional information
-
the transmembrane subunit NarI provides the quinol binding and oxidation site (Q-site)
-
additional information
the transmembrane subunit NarI provides the quinol binding and oxidation site (Q-site)
-
Please wait a moment until the data is sorted. This message will disappear when the data is sorted.
METALS and IONS
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
Fe
Fe2+
Mo
Molybdenum
Fe
complete coordination of the four Fe-S centers of the beta-subunit from Escherichia coli nitrate reductase
Fe
-
coordination model for the four [Fe-S] centres of the electron-transfer subunit NarH, coordination scheme of the [Fe-S] clusters, functional role of [Fe-S] centres
Fe
cysteine arrangements typical of iron-sulfur centers are found in the NarH polypeptide. This suggests that the latter is an electron transfer unit of the nitrate reductase complex
Fe
domain I of subunit NarG holds the [4Fe-4S] cluster FS0. The coordination scheme of FS0 is: His50, Cys54, Cys58, Cys93. NarH contains three [4Fe-4S] clusters, FS1, FS2, FS3 and one [3Fe-4S] cluster, FS4
Fe
domain I of the catalytic subunit NadG holds the [4Fe-4S] cluster FS0
Fe
-
the 230000 Da complex contains 13 atoms iron and 12 atoms labile sulfur/molecules
Fe
-
the catalytic subunit of Escherichia coli nitrate reductase A contains a [4Fe-4S] cluster with a high-spin ground state
Fe
-
the four iron-sulfur centers of nitrate reductase A belong to two classes with markedly different redox potentials. The high-potential group comprises a [3Fe-4S] and a [4Fe-4S] cluster whose midpoint potentials are +60 mV and +80 mV, respectively. Although these centers are magnetically isolated, they are coupled by a significant anticooperative redox interaction of about 50 mV. The [4Fe-4S]1+ center occurs in two different conformations as shown by its composite EPR spectrum. The low-potential group contains two [4Fe-4S] clusters with more typical redox potentials (-200 mV and -400 mV). In the fully reduced state, the three [4Fe-4S]1+ centers are magnetically coupled. The iron-sulfur centers nitrate reductase Z and nitrate reductase A, exhibit essentially the same characteristics, except that the midpoint potentials of the high-potential centers of nitrate reductase Z appear negatively shifted by about 100 mV. A correspondence between the high-potential iron-sulfur clusters of the two enzymes can be proposed
Fe2+
the enzyme binds one [4Fe-4S] cluster per subunit
Mo
-
the enzyme contains a molybdenum cofactor. The enzyme-specific chaperone NarJ coordinates assembly and molybdenum cofactor acquisition of the heterotrimeric enzyme during the biogenesis process
Mo
the enzyme uses a molybdo-bis(molybdopterin guanine dinucleotide) cofactor for catalytic mechanism
Mo
-
the enzyme possesses a molybdopterin guanine dinucleotide active center. Two forms of the molybdenum center, high- and low-pH, are detectable by electron paramagnetic resonance spectroscopy
Molybdenum
the enzyme contains one molybdenum-bis(molybdopterin guanine dinucleotide) cofactor per subunit
Molybdenum
the enzyme contains one molybdenum-bis(molybdopterin guanine dinucleotide) cofactor per subunit
Molybdenum
the enzyme contains one molybdenum-bis(molybdopterin guanine dinucleotide) cofactor per subunit
Please wait a moment until the data is sorted. This message will disappear when the data is sorted.
INHIBITOR
ORGANISM
UNIPROT
COMMENTARY
LITERATURE