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Information on EC 1.13.11.24 - quercetin 2,3-dioxygenase
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1.13.11.24 quercetin 2,3-dioxygenaseIUBMB Comments
The enzyme from Aspergillus sp. is a copper protein whereas that from Bacillus subtilis contains iron. Quercetin is a flavonol (5,7,3',4'-tetrahydroxyflavonol).
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The enzyme appears in viruses and cellular organisms
Synonyms
pirin, quercetinase, quercetin 2,3-dioxygenase, 2,3qd, 2,3-qd, flavonol 2,4-dioxygenase, mn-qdo, vdqase, quercetin dioxygenase, quercetin 2,4-dioxygenase, 
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SYNONYM 
ORGANISM
UNIPROT
COMMENTARY 
LITERATURE
cupin domain-containing protein
flavonol 2,4-dioxygenase
flavonol 2,4-oxygenase
-
-
-
-
QdoI
QueD
quercetinase
type III extradiol dioxygenase
VdQase
quercetinase
-
-
-
-
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REACTION
REACTION DIAGRAM
COMMENTARY
ORGANISM
UNIPROT
LITERATURE
quercetin + O2 = 2-(3,4-dihydroxybenzoyloxy)-4,6-dihydroxybenzoate + CO + H+
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-
-
-
quercetin + O2 = 2-(3,4-dihydroxybenzoyloxy)-4,6-dihydroxybenzoate + CO + H+
EPR study, mechanism, N of His112 is the axial ligand of type II copper site
quercetin + O2 = 2-(3,4-dihydroxybenzoyloxy)-4,6-dihydroxybenzoate + CO + H+
hybrid density functional theory study on mechanism, dioxygen attack on copper is energetically preferred
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quercetin + O2 = 2-(3,4-dihydroxybenzoyloxy)-4,6-dihydroxybenzoate + CO + H+
structure-function analysis of the active site
quercetin + O2 = 2-(3,4-dihydroxybenzoyloxy)-4,6-dihydroxybenzoate + CO + H+
study on mobility and flexibility of substrate cavity, molecular dynamics simulations
quercetin + O2 = 2-(3,4-dihydroxybenzoyloxy)-4,6-dihydroxybenzoate + CO + H+
possible reaction mechanisms and pathways, kinetics, detailed overview
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quercetin + O2 = 2-(3,4-dihydroxybenzoyloxy)-4,6-dihydroxybenzoate + CO + H+
reaction mechanism, overview. Quantum mechanics/molecular mechanics (QM/MM) and QM-only study on the oxidative ring-cleaving reaction of quercetin catalyzed by quercetin 2,4-dioxygenase, i.e. 2,4-QD, which has a mononuclear type 2 copper center and incorporates two oxygen atoms at C2 and C4 positions of the substrate. Dioxygen is more likely to bind to a Cu2+ ion than to a substrate radical, involving the dissociation of the substrate from the copper ion. Then a Cu2+-alkylperoxo complex can be generated. Steric effects of the protein environment contribute to maintain the orientation of the substrate dissociated from the copper center. A prior rearrangement of the Cu2+-alkylperoxo complex and a subsequent hydrogen bond switching assisted by the movement of Glu73 can facilitate formation of an endoperoxide intermediate selectively. Reaction mechanism for endoperoxide formation, overview
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quercetin + O2 = 2-(3,4-dihydroxybenzoyloxy)-4,6-dihydroxybenzoate + CO + H+
the enzyme incorporates both atoms of dioxygen into the substrate by cleaving the central heterocycle ring and releasing CO. The enzyme activates quercetin through deprotonation and the proton acceptor-Glu69 needs to reorient for the reaction to proceed. Energy profiles and reaction schemes for nonenzymatic nitroxygenation of quercetin monoanion. Transient and intermediate structures, catalytic mechaanism, detailed overview
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REACTION TYPE
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
oxidation
-
-
-
-
redox reaction
-
-
-
-
reduction
-
-
-
-
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PATHWAY SOURCE
PATHWAYS
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-
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SYSTEMATIC NAME
IUBMB Comments
quercetin:oxygen 2,3-oxidoreductase (decyclizing)
The enzyme from Aspergillus sp. is a copper protein whereas that from Bacillus subtilis contains iron. Quercetin is a flavonol (5,7,3',4'-tetrahydroxyflavonol).
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CAS REGISTRY NUMBER
COMMENTARY
9075-67-6
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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
3,7,3',4'-tetrahydroxyflavone + O2
?
-
35% of the activity with quercetin, Co-QueD, 15% of the activity with quercetin, Ni-QueD
-
-
?
morin + O2
?
i.e. 3,5,7,2',4'-pentahydroxyflavone, 1.7% of the activity with quercetin
-
-
?
3,5,7,2',4'-pentahydroxyflavone + O2
?
-
5.5% of the activity with quercetin, Co-QueD, 0.9% of the activity with quercetin, Ni-QueD
-
-
?
3,5,7,2',4'-pentahydroxyflavone + O2
?
Streptomyces sp. FLA / DSM 41951
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5.5% of the activity with quercetin, Co-QueD, 0.9% of the activity with quercetin, Ni-QueD
-
-
?
3,5,7,3',4',5'-hexahydroxyflavone + O2
?
-
77% of the activity with quercetin, Co-QueD, 46% of the activity with quercetin, Ni-QueD
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-
?
3,5,7,3',4',5'-hexahydroxyflavone + O2
?
Streptomyces sp. FLA / DSM 41951
-
77% of the activity with quercetin, Co-QueD, 46% of the activity with quercetin, Ni-QueD
-
-
?
3,5,7,4'-tetrahydroxyflavone + O2
?
-
43% of the activity with quercetin, Co-QueD, 29% of the activity with quercetin, Ni-QueD
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-
?
3,5,7,4'-tetrahydroxyflavone + O2
?
Streptomyces sp. FLA / DSM 41951
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43% of the activity with quercetin, Co-QueD, 29% of the activity with quercetin, Ni-QueD
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-
?
3,5,7-trihydroxyflavone + O2
?
-
13% of the activity with quercetin, Co-QueD, 16% of the activity with quercetin, Ni-QueD
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-
?
3,5,7-trihydroxyflavone + O2
?
Streptomyces sp. FLA / DSM 41951
-
13% of the activity with quercetin, Co-QueD, 16% of the activity with quercetin, Ni-QueD
-
-
?
fisetin + O2
2-[[(3,4-dihydroxyphenyl)carbonyl]oxy]-4-hydroxybenzoate + CO
-
1.22% activity compared to quercetin
-
-
?
fisetin + O2
2-[[(3,4-dihydroxyphenyl)carbonyl]oxy]-4-hydroxybenzoate + CO
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1.22% activity compared to quercetin
-
-
?
fisetin + O2
?
i.e. 3,7,3',4'-tetrahydroxyflavone, 23% of the activity with quercetin
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-
?
fisetin + O2
?
Streptomyces sp. FLA / DSM 41951
i.e. 3,7,3',4'-tetrahydroxyflavone, 23% of the activity with quercetin
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-
?
galangin + O2
2,4-dihydroxy-6-[(phenylcarbonyl)oxy]benzoate + CO
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110% activity compared to quercetin
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-
?
galangin + O2
2,4-dihydroxy-6-[(phenylcarbonyl)oxy]benzoate + CO
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110% activity compared to quercetin
-
-
?
galangin + O2
?
i.e. 3,5,7-trihydroxyflavone, 28% of the activity with quercetin
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-
?
galangin + O2
?
Streptomyces sp. FLA / DSM 41951
i.e. 3,5,7-trihydroxyflavone, 28% of the activity with quercetin
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-
?
kaempferol + O2
?
activity is 2.18fold higher than with quercetin
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-
?
kaempferol + O2
?
i.e. 3,5,7,4'-tetrahydroxyflavone. 70% of the activity with quercetin
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-
?
myricetin + O2
?
i.e. 3,5,7,3',4',5'-hexahydroxyflavone. 49% of the activity with quercetin
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-
?
myricetin + O2
?
Streptomyces sp. FLA / DSM 41951
i.e. 3,5,7,3',4',5'-hexahydroxyflavone. 49% of the activity with quercetin
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-
?
quercetin + O2
2-(3,4-dihydroxybenzoyloxy)-4,6-dihydroxybenzoate + CO
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-
-
?
quercetin + O2
2-(3,4-dihydroxybenzoyloxy)-4,6-dihydroxybenzoate + CO
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-
-
?
quercetin + O2
2-(3,4-dihydroxybenzoyloxy)-4,6-dihydroxybenzoate + CO
transcription of queD is triggered by quercetin and its 3-O-rhamnosylglucoside rutin, but not by the flavonol morin (3,5,7,2',4'-pentahydroxyflavone), the presumed quercetin degradation products protocatechuate and 2,4,6-trihydroxybenzoate or the sugars rhamnose and glucose. Quercetin-induced queD expression is not influenced by the presence of Ni(II)
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-
?
quercetin + O2
2-(3,4-dihydroxybenzoyloxy)-4,6-dihydroxybenzoate + CO
Streptomyces sp. FLA / DSM 41951
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-
?
quercetin + O2
2-(3,4-dihydroxybenzoyloxy)-4,6-dihydroxybenzoate + CO
Streptomyces sp. FLA / DSM 41951
transcription of queD is triggered by quercetin and its 3-O-rhamnosylglucoside rutin, but not by the flavonol morin (3,5,7,2',4'-pentahydroxyflavone), the presumed quercetin degradation products protocatechuate and 2,4,6-trihydroxybenzoate or the sugars rhamnose and glucose. Quercetin-induced queD expression is not influenced by the presence of Ni(II)
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-
?
quercetin + O2
2-(3,4-dihydroxybenzoyloxy)-4,6-dihydroxybenzoate + CO + H+
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?
quercetin + O2
2-(3,4-dihydroxybenzoyloxy)-4,6-dihydroxybenzoate + CO + H+
the mechanism consists in four successive steps, the first one concerns addition of O2 on the C2 carbon atom, the second corresponds to the closure of the endoperoxo intermediate. In the two last steps, bonds are broken to produce the depside and carbon monoxide. Addition of dioxygen on the C2 atom (step 1) is associated to a pyramidalization at the C2 carbon atom and to a rotation of the B-ring with respect to the conjugated A-C rings. The second step is the rate limiting one and the free energy barriers characterized for the four flavonoids are very close, reaching about 24 kcal/mol. Differences in the values are not significant enough to be exploited to rationalize the nonlinear evolution of the degradation rate. Moreover, the relatively high energy value is expected to be lowered by taking into account the whole environment
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-
?
quercetin + O2
2-(3,4-dihydroxybenzoyloxy)-4,6-dihydroxybenzoate + CO + H+
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cleavages of the C2-C3 and C3-C4 bonds of quercetin (Que) catalyzed by 2,4-QDs
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?
quercetin + O2
2-(3,4-dihydroxybenzoyloxy)-4,6-dihydroxybenzoate + CO + H+
-
-
-
-
?
quercetin + O2
2-(3,4-dihydroxybenzoyloxy)-4,6-dihydroxybenzoate + CO + H+
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quercetin dioxygenase catalyzes the oxidation of the flavonol quercetin with dioxygen, cleaving the central heterocyclic ring and releasing CO
-
-
?
quercetin + O2
2-(3,4-dihydroxybenzoyloxy)-4,6-dihydroxybenzoate + CO + H+
-
-
-
-
?
quercetin + O2
2-(3,4-dihydroxybenzoyloxy)-4,6-dihydroxybenzoate + CO + H+
-
-
-
-
?
quercetin + O2
2-(3,4-dihydroxybenzoyloxy)-4,6-dihydroxybenzoate + CO + H+
-
-
-
?
quercetin + O2
2-(3,4-dihydroxybenzoyloxy)-4,6-dihydroxybenzoate + CO + H+
Streptomyces sp. FLA / DSM 41951
-
-
-
-
?
quercetin + O2
2-(3,4-dihydroxybenzoyloxy)-4,6-dihydroxybenzoate + CO + H+
-
-
-
?
quercetin + O2
2-(3,4-dihydroxybenzoyloxy)-4,6-dihydroxybenzoate + CO + H+
-
-
-
?
quercetin + O2
2-protocatechoylphloroglucinolcarboxylate + CO
-
-
-
-
?
quercetin + O2
2-protocatechoylphloroglucinolcarboxylate + CO
-
-
-
?
quercetin + O2
2-protocatechoylphloroglucinolcarboxylate + CO
-
-
-
?
quercetin + O2
2-protocatechoylphloroglucinolcarboxylate + CO
-
low activity
-
-
?
quercetin + O2
2-protocatechoylphloroglucinolcarboxylate + CO
-
quercetin is a flavonol
-
-
?
quercetin + O2
2-protocatechoylphloroglucinolcarboxylate + CO
-
-
-
-
?
quercetin + O2
2-protocatechoylphloroglucinolcarboxylate + CO
-
low activity
-
-
?
quercetin + O2
2-protocatechoylphloroglucinolcarboxylate + CO
-
-
-
-
?
quercetin + O2
2-protocatechoylphloroglucinolcarboxylate + CO
-
low activity
-
-
?
quercetin + O2
2-protocatechoylphloroglucinolcarboxylate + CO
-
-
-
-
?
quercetin + O2
2-protocatechoylphloroglucinolcarboxylate + CO
-
low activity
-
-
?
quercetin + O2
2-protocatechoylphloroglucinolcarboxylate + CO
-
-
-
-
?
quercetin + O2
2-protocatechoylphloroglucinolcarboxylate + CO
-
low activity
-
-
?
quercetin + O2
2-protocatechoylphloroglucinolcarboxylate + CO
-
-
-
-
?
quercetin + O2
2-protocatechoylphloroglucinolcarboxylate + CO
-
low activity
-
-
?
quercetin + O2
2-protocatechoylphloroglucinolcarboxylate + CO
-
-
-
-
?
quercetin + O2
2-protocatechoylphloroglucinolcarboxylate + CO
-
-
-
-
?
quercetin + O2
2-protocatechoylphloroglucinolcarboxylate + CO
-
-
-
?
quercetin + O2
2-protocatechoylphloroglucinolcarboxylate + CO
-
-
-
?
quercetin + O2
2-protocatechoylphloroglucinolcarboxylate + CO
-
-
-
-
?
quercetin + O2
2-protocatechoylphloroglucinolcarboxylate + CO
-
100% activity
-
-
?
quercetin + O2
2-protocatechoylphloroglucinolcarboxylate + CO
-
-
-
-
?
quercetin + O2
2-protocatechoylphloroglucinolcarboxylate + CO
-
100% activity
-
-
?
quercetin + O2
2-protocatechoylphloroglucinolcarboxylate + CO
-
-
-
?
quercetin + O2
2-protocatechoylphloroglucinolcarboxylate + CO
Streptomyces sp. FLA / DSM 41951
-
-
-
-
?
quercetin + O2
2-protocatechoylphloroglucinolcarboxylate + CO
Streptomyces sp. FLA / DSM 41951
-
-
-
?
tamarixetin + O2
2,4-dihydroxy-6-[[(3-hydroxy-4-methoxyphenyl)carbonyl]oxy]benzoate + CO
-
82.4% activity compared to quercetin
-
-
?
tamarixetin + O2
2,4-dihydroxy-6-[[(3-hydroxy-4-methoxyphenyl)carbonyl]oxy]benzoate + CO
-
82.4% activity compared to quercetin
-
-
?
additional information
?
-
quercetin 2,3-dioxygenase is a copper-containing enzyme that catalyzes the insertion of molecular oxygen into polyphenolic flavonols
-
-
?
additional information
?
-
-
quercetin 2,3-dioxygenase is a copper-containing enzyme that catalyzes the insertion of molecular oxygen into polyphenolic flavonols
-
-
?
additional information
?
-
-
the enzyme opens up two C-C bonds of the heterocyclic ring of quercetin, a widespread plant flavonol
-
-
?
additional information
?
-
-
quercetin 2,3-dioxygenase activates molecular oxygen to catalyze the oxygenative ring-opening reaction of the O-heterocycle of quercetin to the corresponding depside (phenolic carboxylic acid esters) and carbon monoxide
-
-
?
additional information
?
-
-
a flavonolate ion (fla-, deprotonated substrate) is bound through the 3-hydroxy group to the copper(II) ion, which exhibits a distorted squarepyramidal geometry. The bound substrate is stabilized by Glu73 through a hydrogen-bonding interaction. Synthesis of a set of copper(II) complexes [CuIILn(AcO)] and their flavonolate adducts [CuIILn(fla)] with the series of carboxyl-group-containing ligands LnH, the treatment of the ligands with CuII(OAc)2xH2O gives the corresponding mononuclear copper(II) complexes [CuIILn(OAc)], dioxygenation of flavonol catalyzed by the binary complexes [CuIILn(AcO)] (multiturnover reaction), kinetics, overview
-
-
?
additional information
?
-
-
computational study on the dioxygenation reaction of the substrate flavonolate (fla) by a synthetic model complex and related species mimicking quercetin 2,4-dioxygenases, overview. The reaction mechanism obtained for the present biomimetic complexes is substantially different from the plausible enzymatic reaction. All model complexes favor a single electron transfer from flavonolate to dioxygen over a valence tautomerism, and a subsequent intersystem crossing and a ring-closure lead to a formation of a 1,2-dioxetane intermediate instead of undergoing a direct formation of a precursor endoperoxide. The generation of the 1,2-dioxetane intermediate is shown to be the rate-determining step and inclusion of a carboxylate co-ligand can enhance the reactivity, rendering this process barrier-free. Proposal of a pathway, which can circumvent a non-enzymatic reaction by involving conversion from the 1,2-dioxetane to the endoperoxide with lower barriers
-
-
?
additional information
?
-
-
the enzyme opens up two C-C bonds of the heterocyclic ring of quercetin, a widespread plant flavonol
-
-
?
additional information
?
-
-
Mn-QDO in absence of O2 shows ability to react with nitroxyl (HNO)-singly reduced form of NO. HNO is incorporated into quercetin in the same manneras dioxygen, yet the reaction is strictly regioselective, as the only product is 2-((3,4-dihydroxyphenyl)(imino)methoxy)-4,6-dihydroxybenzoate
-
-
?
additional information
?
-
-
high level of pirin leads to the resistance of poliovirus replication to quercetin by inactivating this flavonoid
-
-
?
additional information
?
-
flavonol, morin, 3,6-dihydroxyflavone and 3,7-dihydroxyflavone are transformed at a rate of less than 1% of that found for quercetin
-
-
?
additional information
?
-
-
flavonol, morin, 3,6-dihydroxyflavone and 3,7-dihydroxyflavone are transformed at a rate of less than 1% of that found for quercetin
-
-
?
additional information
?
-
-
the enzyme opens up two C-C bonds of the heterocyclic ring of quercetin, a widespread plant flavonol
-
-
?
additional information
?
-
-
the enzyme opens up two C-C bonds of the heterocyclic ring of quercetin, a widespread plant flavonol
-
-
?
additional information
?
-
Streptomyces sp. FLA / DSM 41951
-
the enzyme opens up two C-C bonds of the heterocyclic ring of quercetin, a widespread plant flavonol
-
-
?
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
quercetin + O2
2-(3,4-dihydroxybenzoyloxy)-4,6-dihydroxybenzoate + CO
-
-
-
?
quercetin + O2
2-(3,4-dihydroxybenzoyloxy)-4,6-dihydroxybenzoate + CO
Streptomyces sp. FLA / DSM 41951
-
-
-
?
quercetin + O2
2-(3,4-dihydroxybenzoyloxy)-4,6-dihydroxybenzoate + CO + H+
-
-
-
-
?
quercetin + O2
2-(3,4-dihydroxybenzoyloxy)-4,6-dihydroxybenzoate + CO + H+
-
-
-
-
?
quercetin + O2
2-(3,4-dihydroxybenzoyloxy)-4,6-dihydroxybenzoate + CO + H+
-
quercetin dioxygenase catalyzes the oxidation of the flavonol quercetin with dioxygen, cleaving the central heterocyclic ring and releasing CO
-
-
?
quercetin + O2
2-(3,4-dihydroxybenzoyloxy)-4,6-dihydroxybenzoate + CO + H+
-
-
-
-
?
quercetin + O2
2-(3,4-dihydroxybenzoyloxy)-4,6-dihydroxybenzoate + CO + H+
-
-
-
-
?
quercetin + O2
2-(3,4-dihydroxybenzoyloxy)-4,6-dihydroxybenzoate + CO + H+
-
-
-
?
quercetin + O2
2-(3,4-dihydroxybenzoyloxy)-4,6-dihydroxybenzoate + CO + H+
Streptomyces sp. FLA / DSM 41951
-
-
-
-
?
quercetin + O2
2-(3,4-dihydroxybenzoyloxy)-4,6-dihydroxybenzoate + CO + H+
-
-
-
?
quercetin + O2
2-(3,4-dihydroxybenzoyloxy)-4,6-dihydroxybenzoate + CO + H+
-
-
-
?
quercetin + O2
2-protocatechoylphloroglucinolcarboxylate + CO
-
-
-
-
?
quercetin + O2
2-protocatechoylphloroglucinolcarboxylate + CO
-
-
-
?
quercetin + O2
2-protocatechoylphloroglucinolcarboxylate + CO
-
-
-
?
quercetin + O2
2-protocatechoylphloroglucinolcarboxylate + CO
-
quercetin is a flavonol
-
-
?
quercetin + O2
2-protocatechoylphloroglucinolcarboxylate + CO
-
-
-
-
?
quercetin + O2
2-protocatechoylphloroglucinolcarboxylate + CO
-
-
-
-
?
quercetin + O2
2-protocatechoylphloroglucinolcarboxylate + CO
-
-
-
-
?
quercetin + O2
2-protocatechoylphloroglucinolcarboxylate + CO
-
-
-
-
?
quercetin + O2
2-protocatechoylphloroglucinolcarboxylate + CO
-
-
-
-
?
quercetin + O2
2-protocatechoylphloroglucinolcarboxylate + CO
-
-
-
-
?
quercetin + O2
2-protocatechoylphloroglucinolcarboxylate + CO
-
-
-
-
?
quercetin + O2
2-protocatechoylphloroglucinolcarboxylate + CO
-
-
-
?
quercetin + O2
2-protocatechoylphloroglucinolcarboxylate + CO
-
-
-
?
quercetin + O2
2-protocatechoylphloroglucinolcarboxylate + CO
-
-
-
-
?
quercetin + O2
2-protocatechoylphloroglucinolcarboxylate + CO
Streptomyces sp. FLA / DSM 41951
-
-
-
-
?
additional information
?
-
quercetin 2,3-dioxygenase is a copper-containing enzyme that catalyzes the insertion of molecular oxygen into polyphenolic flavonols
-
-
?
additional information
?
-
-
quercetin 2,3-dioxygenase is a copper-containing enzyme that catalyzes the insertion of molecular oxygen into polyphenolic flavonols
-
-
?
additional information
?
-
-
the enzyme opens up two C-C bonds of the heterocyclic ring of quercetin, a widespread plant flavonol
-
-
?
additional information
?
-
-
the enzyme opens up two C-C bonds of the heterocyclic ring of quercetin, a widespread plant flavonol
-
-
?
additional information
?
-
-
high level of pirin leads to the resistance of poliovirus replication to quercetin by inactivating this flavonoid
-
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?
additional information
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the enzyme opens up two C-C bonds of the heterocyclic ring of quercetin, a widespread plant flavonol
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additional information
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the enzyme opens up two C-C bonds of the heterocyclic ring of quercetin, a widespread plant flavonol
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additional information
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Streptomyces sp. FLA / DSM 41951
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the enzyme opens up two C-C bonds of the heterocyclic ring of quercetin, a widespread plant flavonol
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COFACTOR
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
IMAGE
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METALS and IONS
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
Co2+
copper
Cu
Cu2+
Fe2+
HNO
-
nitrosyl hydride replaces dioxygen in nitroxygenase activity of manganese quercetin dioxygenase resulting in the incorporation of both N and O atoms into the product. Turnover is demonstrated by consumption of quercetin and other related substrates under anaerobic conditions in the presence of HNO-releasing compounds and the enzyme. As with dioxygenase activity, a nonenzymatic base-catalyzed reaction of quercetin with HNO isobserved above pH 7, but no enhancement of this basal reactivity is found upon addition of divalent metal salts. Unique and regioselective N-containing products are characterized by MS analysis for both the enzymatic and nonenzymatic reactions
Iron
Mn2+
Ni2+
Nickel
dioxygen shows two binding modes to the nickel ion, which can convert each other. Due to the overlap between the vacant d orbitals of nickel and the lone pair p orbitals of dioxygen and quercetin, electron transfer occurs from quercetin to dioxygen via the nickel center. Both dioxygen and quercetin can be activated by their binding to the nickel ion. The triplet reactant complex favors the catalytic reaction, and the whole reaction contains four elementary steps. A nonchemical process, the Op-Od bond rotation along the nickel center, is suggested to be rate-limiting with a free energy barrier of 19.9 kcal/mol
Zn2+
additional information
Co2+
-
Co2+ salt addition increases the activity of quercetin 2,3-dioxygenase 24fold. The Escherichia coli cultures were grown at 37°C and 200 rpm for 6 h, induced with isopropyl beta-D-thiogalactopyanoside to a final concentraton of 50 mg/l in the presence of 10 microM CoCl2, and allow to grow additional 4 h at 25°C. The protein contains 0.65-0.8 atom of cobalt and 0.1 atom of iron per subunit.
Co2+
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supplementing the cultures of strain FLA with CoCl2 results in 1.6fold higher quercetinase activity in crude extracts
Cu
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probably belongs to the nonblue class, two atoms per molecule of enzyme
Cu2+
required, enzyme-bound, structure, overview. Manual docking, different geometries of the copper site
Cu2+
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required, mononuclear copper(II) active site, binding structure, X-ray diffraction and NMR analysis, overview. Direct coordinative interaction between copper(II) ion and the carboxylate group of Glu73. Complexes modeling, overview
Cu2+
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required, the copper ion is mainly coordinated by three His residues and a water molecule in a distorted tetrahedral geometry. In a minor form, the metal is penta-coordinated by three His, a glutamate, and an aquo ligand in a trigonal bipyramidal geometry. The major role of the activesite metal ion could be to correctly position the substrate and to stabilize transition states and intermediates rather than to mediate electron transfer
Cu2+
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required, a flavonolate ion (fla-, deprotonated substrate) is bound through the 3-hydroxy group to the copper(II) ion, which exhibits a distorted squarepyramidal geometry
Cu2+
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the enzyme has a mononuclear type 2 copper center, steric effects of the protein environment contribute to maintain the orientation of the substrate dissociated from the copper center. A prior rearrangement of the Cu2+-alkylperoxo complex and a subsequent hydrogen bond switching assisted by the movement of Glu73 can facilitate formation of an endoperoxide intermediate selectively
Cu2+
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Cu2+ salt addition increases the activity of quercetin 2,3-dioxygenase 1.4fold. The Escherichia coli cultures were grown at 37°C and 200 rpm for 6 h, induced with isopropyl beta-D-thiogalactopyanoside to a final concentraton of 50 mg/l in the presence of 10 microM CuCl2, and allow to grow additional 4 h at 25°C.
Cu2+
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activates, Cu-QDO, during the reaction mechanism of Cu-QDO dioxygen binds to the metal ion of the Cu-QDO-quercetin complex, yielding a Cu2+-superoxo quercetin radical intermediate, which then forms a Cu2+-alkylperoxo complex, the alkylperoxo complex evolves into endoperoxide intermediate that decomposes to the product
Cu2+
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required, the major role of the activesite metal ion could be to correctly position the substrate and to stabilize transition states and intermediates rather than to mediate electron transfer
Iron
different coordination geometry in the two active sites of the dimer
Iron
when the metal cofactor is replaced by an iron ion, the rate-limiting step switches from the Op-Od bond rotation to the collapse of the five-membered ring intermediate, corresponding to a free energy barrier of 30.3 kcal/mol
Mn2+
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Mn2+ salt addition increases the activity of quercetin 2,3-dioxygenase 35fold. The Escherichia coli cultures were grown at 37°C and 200 rpm for 6 h, induced with isopropyl beta-D-thiogalactopyanoside to a final concentraton of 50 mg/l in the presence of 10 microM MnSO4, and allow to grow additional 4 h at 25°C. The protein containes 1.6-1.9 atoms of Mn/subunit.
Mn2+
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activates, Mn-QDO, Mn2+ i the preferred metal ion. Mn-QDO in absence of O2 shows ability to react with nitroxyl (HNO)-singly reduced form of NO. HNO is incorporated into quercetin in the same manner as dioxygen, yet the reaction is strictly regioselective, as the only product is 2-((3,4-dihydroxyphenyl)(imino) methoxy)-4,6-dihydroxybenzoate
Ni2+
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Ni2+ salt addition increases the activity of quercetin 2,3-dioxygenase 2.6fold. The Escherichia coli cultures were grown at 37°C and 200 rpm for 6 h, induced with isopropyl beta-D-thiogalactopyanoside to a final concentraton of 50 mg/l in the presence of 10 microM NiCl2, and allow to grow additional 4 h at 25°C.
Ni2+
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supplementing the cultures of strain FLA with NiCl2 results in 6.1fold higher quercetinase activity in crude extracts