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Information on EC 1.14.14.20 - phenol 2-monooxygenase (FADH2)
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EC Tree
1.14.14.20 phenol 2-monooxygenase (FADH2)IUBMB Comments
The enzyme catalyses the ortho-hydroxylation of simple phenols into the corresponding catechols. It accepts 4-methylphenol, 4-chlorophenol, and 4-fluorophenol as well as 4-nitrophenol, 3-nitrophenol, and resorcinol . The enzyme is part of a two-component system that also includes an NADH-dependent flavin reductase. It is strictly dependent on FADH2 and does not accept FMNH2 [1,3]. cf. EC 1.14.13.7, phenol 2-monooxygenase (NADPH).
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Word Map
- 1.14.14.20
-
two-component
- rhodococcus
- thermoglucosidasius
- catechols
- erythropolis
- isoalloxazine
-
prosthetic
-
nadh-dependent
- reductases
- fmnh2
- hydroxylases
-
ping-pong
-
homotetramer
-
hydride
- environmental protection
- 4-hydroxyphenylacetate
-
fad-containing
- synthesis
- styrene
The enzyme appears in viruses and cellular organisms
Synonyms
phea2, phea1, flavin reductase phea2, 
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SYNONYM 
ORGANISM
UNIPROT
COMMENTARY 
LITERATURE
FAD reductase
flavin reductase PheA2
PheA
PheA1
PheA2
phenol hydroxylase
PheA
-
the two-protein system phenol hydroxylase, encoded by the pheA1 and pheA2 genes, consists of an oxygenase (PheA1) and a flavin reductase (PheA2)
PheA
-
the two-protein system phenol hydroxylase, encoded by the pheA1 and pheA2 genes, consists of an oxygenase (PheA1) and a flavin reductase (PheA2)
-
PheA1
-
-
-
-
phenol hydroxylase
-
the two-protein system, encoded by the pheA1 and pheA2 genes, consists of an oxygenase (PheA1) and a flavin reductase (PheA2)
phenol hydroxylase
-
the two-protein system, encoded by the pheA1 and pheA2 genes, consists of an oxygenase (PheA1) and a flavin reductase (PheA2)
-
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REACTION
REACTION DIAGRAM
COMMENTARY
ORGANISM
UNIPROT
LITERATURE
phenol + FADH2 + O2 = catechol + FAD + H2O
-
-
-
-
phenol + FADH2 + O2 = catechol + FAD + H2O
smaller flavin reductase PheA2 component catalyzes the NADH-dependent reduction of free FAD according to a ping pong bisubstrate-biproduct mechanism
-
phenol + FADH2 + O2 = catechol + FAD + H2O
smaller flavin reductase PheA2 component catalyzes the NADH-dependent reduction of free FAD according to a ping pong bisubstrate-biproduct mechanism
-
-
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SYSTEMATIC NAME
IUBMB Comments
phenol,FADH2:oxygen oxidoreductase (2-hydroxylating)
The enzyme catalyses the ortho-hydroxylation of simple phenols into the corresponding catechols. It accepts 4-methylphenol, 4-chlorophenol, and 4-fluorophenol [1] as well as 4-nitrophenol, 3-nitrophenol, and resorcinol [3]. The enzyme is part of a two-component system that also includes an NADH-dependent flavin reductase. It is strictly dependent on FADH2 and does not accept FMNH2 [1,3]. cf. EC 1.14.13.7, phenol 2-monooxygenase (NADPH).
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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
4-methylphenol + FADH2 + O2
4-methylcatechol + FAD + H2O
-
-
-
?
catechol + riboflavin + H2O
phenol + reduced riboflavin + O2
-
-
-
r
2,4-dichlorophenol + FADH2 + O2
2,4-dichlorocatechol + FAD + H2O
-
-
-
?
2,4-dichlorophenol + FADH2 + O2
2,4-dichlorocatechol + FAD + H2O
-
-
-
?
2-chlorophenol + FADH2 + O2
2-chlorocatechol + FAD + H2O
-
-
-
?
2-chlorophenol + FADH2 + O2
2-chlorocatechol + FAD + H2O
poor substrate for isozyme PheA1(1)
-
-
?
2-chlorophenol + FADH2 + O2
2-chlorocatechol + FAD + H2O
-
-
-
?
2-chlorophenol + FADH2 + O2
2-chlorocatechol + FAD + H2O
poor substrate for isozyme PheA1(1)
-
-
?
3-nitrophenol + NAD(P)H + H+ + O2
? + NAD(P)+ + H2O
-
-
-
?
3-nitrophenol + NAD(P)H + H+ + O2
? + NAD(P)+ + H2O
-
-
-
?
4-chlorophenol + FADH2 + O2
4-chlorocatechol + FAD + H2O
-
-
-
?
4-chlorophenol + FADH2 + O2
4-chlorocatechol + FAD + H2O
-
-
-
?
4-nitrophenol + NAD(P)H + H+ + O2
? + NAD(P)+ + H2O
-
-
-
?
4-nitrophenol + NAD(P)H + H+ + O2
? + NAD(P)+ + H2O
-
-
-
?
phenol + FADH2 + O2
catechol + FAD + H2O
-
-
-
?
phenol + FADH2 + O2
catechol + FAD + H2O
-
-
-
?
phenol + FADH2 + O2
catechol + FAD + H2O
-
-
-
?
phenol + FADH2 + O2
catechol + FAD + H2O
-
a two-component enzyme system: the smaller flavin reductase PheA2 component catalyzes the NADH-dependent reduction of free FAD according to a ping pong bisubstrate-biproduct mechanism. The reduced FAD is then used by the larger oxygenase component PheA1 to hydroxylate phenols to the corresponding catechols
-
-
?
phenol + FADH2 + O2
catechol + FAD + H2O
PheA1 is required for activity, no activity by PheA2 alone. PheA2 acts according to a ping pong bi bi reaction mechanism in which NADH reduces the FAD cofactor, which in turn transfers electrons to the FAD substrate
-
-
?
phenol + FADH2 + O2
catechol + FAD + H2O
-
reactive exogenous FAD substrate binds in the NADH cleft after release of NAD product. PheA2 is able to bind one FAD cofactor and one FAD substrate
-
-
?
phenol + FADH2 + O2
catechol + FAD + H2O
-
a two-component enzyme system: the smaller flavin reductase PheA2 component catalyzes the NADH-dependent reduction of free FAD according to a ping pong bisubstrate-biproduct mechanism. The reduced FAD is then used by the larger oxygenase component PheA1 to hydroxylate phenols to the corresponding catechols
-
-
?
phenol + FADH2 + O2
catechol + FAD + H2O
-
reactive exogenous FAD substrate binds in the NADH cleft after release of NAD product. PheA2 is able to bind one FAD cofactor and one FAD substrate
-
-
?
phenol + FADH2 + O2
catechol + FAD + H2O
-
-
-
?
phenol + FADH2 + O2
catechol + FAD + H2O
-
-
-
?
phenol + FADH2 + O2
catechol + FAD + H2O
PheA1 is required for activity, no activity by PheA2 alone. PheA2 acts according to a ping pong bi bi reaction mechanism in which NADH reduces the FAD cofactor, which in turn transfers electrons to the FAD substrate
-
-
?
phenol + FADH2 + O2
catechol + FAD + H2O
-
-
-
?
phenol + FADH2 + O2
catechol + FAD + H2O
hydroxylation of phenol in vitro requires the presence of both PheA1 and PheA2 components, in addition to NADH and FAD, but the physical interaction between the proteins is not necessary for the reaction, Km for FAD is 0.0134 mM, Km for NADH is 0.0533 mM. The hydroxylation of phenol in vitro depends on the molar ratio of His6PheA2 and His6PheA1 present in the reaction mixture, an increase of the amount of His6PheA1 in the assay results in a higher phenol hydroxylase activity. In the assay, a reductase/oxygenase molar ratio of 1:10 is used
-
-
?
phenol + FADH2 + O2
catechol + FAD + H2O
hydroxylation of phenol in vitro requires the presence of both PheA1 and PheA2 components, in addition to NADH and FAD, but the physical interaction between the proteins is not necessary for the reaction. The hydroxylation of phenol in vitro depends on the molar ratio of His6PheA2 and His6PheA1 present in the reaction mixture, an increase of the amount of His6PheA1 in the assay results in a higher phenol hydroxylase activity. In the assay, a reductase/oxygenase molar ratio of 1:10 is used
-
-
?
phenol + FMNH2 + O2
catechol + FMN + H2O
-
-
-
?
phenol + FMNH2 + O2
catechol + FMN + H2O
-
-
-
?
phenol + NAD(P)H + H+ + O2
catechol + NAD(P)+ + H2O
hydroxylation of phenol in vitro requires the presence of both His6PheA1 and His6PheA2 components, in addition to NADH and FAD, but the physical interaction between the proteins is not necessary for the reaction
-
-
?
phenol + NAD(P)H + H+ + O2
catechol + NAD(P)+ + H2O
hydroxylation of phenol in vitro requires the presence of both His6PheA1 and His6PheA2 components, in addition to NADH and FAD, but the physical interaction between the proteins is not necessary for the reaction
-
-
?
phenol + NADH + H+ + O2
catechol + NAD+ + H2O
the two-protein system phenol hydroxylase consists of an oxygenase (PheA1) and a flavin reductase (PheA2). PheA1 catalyzes the efficient ortho-hydroxylation of phenol to catechol when supplemented with PheA2 and FAD/NADH. PheA1 catalyzes the NADH-dependent reduction of free flavins according to a ping pong bi bi mechanism
-
-
?
phenol + NADH + H+ + O2
catechol + NAD+ + H2O
the two-protein system phenol hydroxylase consists of an oxygenase (PheA1) and a flavin reductase (PheA2). PheA1 catalyzes the efficient ortho-hydroxylation of phenol to catechol when supplemented with PheA2 and FAD/NADH. PheA1 catalyzes the NADH-dependent reduction of free flavins according to a ping pong bi bi mechanism
-
-
?
phenol + NADH + H+ + O2
catechol + NAD+ + H2O
-
-
-
r
phenol + reduced riboflavin + O2
catechol + riboflavin + H2O
-
-
-
?
phenol + reduced riboflavin + O2
catechol + riboflavin + H2O
-
-
-
?
resorcinol + NAD(P)H + H+ + O2
? + NAD(P)+ + H2O
-
-
-
?
resorcinol + NAD(P)H + H+ + O2
? + NAD(P)+ + H2O
-
-
-
?
additional information
?
-
-
enzyme components PheA2 and PheA1 show no protein-protein interaction
-
-
?
additional information
?
-
enzyme components PheA2 and PheA1 show no protein-protein interaction
-
-
?
additional information
?
-
enzyme components PheA2 and PheA1 show no protein-protein interaction
-
-
?
additional information
?
-
-
PheA1 is required for activity of flavin reductase PheA2, no activity by PheA1 or PheA2 alone
-
-
?
additional information
?
-
PheA1 is required for activity of flavin reductase PheA2, no activity by PheA1 or PheA2 alone
-
-
?
additional information
?
-
PheA1 is required for activity of flavin reductase PheA2, no activity by PheA1 or PheA2 alone
-
-
?
additional information
?
-
-
enzyme components PheA2 and PheA1 show no protein-protein interaction
-
-
?
additional information
?
-
enzyme components PheA2 and PheA1 show no protein-protein interaction
-
-
?
additional information
?
-
enzyme components PheA2 and PheA1 show no protein-protein interaction
-
-
?
additional information
?
-
-
PheA1 is required for activity of flavin reductase PheA2, no activity by PheA1 or PheA2 alone
-
-
?
additional information
?
-
PheA1 is required for activity of flavin reductase PheA2, no activity by PheA1 or PheA2 alone
-
-
?
additional information
?
-
PheA1 is required for activity of flavin reductase PheA2, no activity by PheA1 or PheA2 alone
-
-
?
additional information
?
-
the two-component phenol hydroxylase is completely unable to hydroxylate benzoate, 4-hydroxybenzoate, and orcinol
-
-
?
additional information
?
-
the two-component phenol hydroxylase is completely unable to hydroxylate benzoate, 4-hydroxybenzoate, and orcinol
-
-
?
additional information
?
-
the two-component phenol hydroxylase is completely unable to hydroxylate benzoate, 4-hydroxybenzoate, and orcinol
-
-
?
additional information
?
-
the two-component phenol hydroxylase is completely unable to hydroxylate benzoate, 4-hydroxybenzoate, and orcinol
-
-
?
additional information
?
-
-
the two-component phenol hydroxylase is completely unable to hydroxylate benzoate, 4-hydroxybenzoate, and orcinol
-
-
?
additional information
?
-
substrate speccificities of the three isozymes, overview
-
-
?
additional information
?
-
substrate speccificities of the three isozymes, overview
-
-
?
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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
4-methylphenol + FADH2 + O2
4-methylcatechol + FAD + H2O
-
-
-
?
2,4-dichlorophenol + FADH2 + O2
2,4-dichlorocatechol + FAD + H2O
-
-
-
?
2,4-dichlorophenol + FADH2 + O2
2,4-dichlorocatechol + FAD + H2O
-
-
-
?
2-chlorophenol + FADH2 + O2
2-chlorocatechol + FAD + H2O
poor substrate for isozyme PheA1(1)
-
-
?
2-chlorophenol + FADH2 + O2
2-chlorocatechol + FAD + H2O
poor substrate for isozyme PheA1(1)
-
-
?
4-chlorophenol + FADH2 + O2
4-chlorocatechol + FAD + H2O
-
-
-
?
4-chlorophenol + FADH2 + O2
4-chlorocatechol + FAD + H2O
-
-
-
?
phenol + FADH2 + O2
catechol + FAD + H2O
-
-
-
?
phenol + FADH2 + O2
catechol + FAD + H2O
-
-
-
?
phenol + FADH2 + O2
catechol + FAD + H2O
-
-
-
?
phenol + FADH2 + O2
catechol + FAD + H2O
-
a two-component enzyme system: the smaller flavin reductase PheA2 component catalyzes the NADH-dependent reduction of free FAD according to a ping pong bisubstrate-biproduct mechanism. The reduced FAD is then used by the larger oxygenase component PheA1 to hydroxylate phenols to the corresponding catechols
-
-
?
phenol + FADH2 + O2
catechol + FAD + H2O
-
a two-component enzyme system: the smaller flavin reductase PheA2 component catalyzes the NADH-dependent reduction of free FAD according to a ping pong bisubstrate-biproduct mechanism. The reduced FAD is then used by the larger oxygenase component PheA1 to hydroxylate phenols to the corresponding catechols
-
-
?
phenol + FADH2 + O2
catechol + FAD + H2O
-
-
-
?
phenol + FADH2 + O2
catechol + FAD + H2O
-
-
-
?
phenol + FADH2 + O2
catechol + FAD + H2O
-
-
-
?
additional information
?
-
-
enzyme components PheA2 and PheA1 show no protein-protein interaction
-
-
?
additional information
?
-
enzyme components PheA2 and PheA1 show no protein-protein interaction
-
-
?
additional information
?
-
enzyme components PheA2 and PheA1 show no protein-protein interaction
-
-
?
additional information
?
-
-
enzyme components PheA2 and PheA1 show no protein-protein interaction
-
-
?
additional information
?
-
enzyme components PheA2 and PheA1 show no protein-protein interaction
-
-
?
additional information
?
-
enzyme components PheA2 and PheA1 show no protein-protein interaction
-
-
?
additional information
?
-
substrate speccificities of the three isozymes, overview
-
-
?
additional information
?
-
substrate speccificities of the three isozymes, overview
-
-
?
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COFACTOR
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
IMAGE
FAD
PheA2 uses FAD both as a substrate and as a prosthetic group, strictly dependent on, neither FMN nor riboflavin can replace FAD in this reaction. PheA2 is a a homodimer, with each subunit containing a highly fluorescent FAD prosthetic group
FAD
activity of the oxygenase component His6PheA1 of phenol hydroxylase is strictly dependent on FAD
FADH2
FAD is bound to PheA2, binding structure analysis, overview
FADH2
-
PheA2 is a single domain homodimeric protein with each FAD-containing subunit being organized around a six-stranded beta-sheet and a capping alpha-helix. The tightly bound FAD prosthetic group binds near the dimer interface, and the re face of the FAD isoalloxazine ring is fully exposed to solvent, binding structure, overview
NADH
PheA2 uses NADH in order to reduce FAD, according to a random sequential kinetic mechanism
NADH
-
addition of NADH to crystalline PheA2 reduces the flavin cofactor, the NAD product is bound in a wide solvent-accessible groove adopting an unusual folded conformation with ring stacking, binding structure, overview
NADH
NADH is a much better coenzyme for PheA2 than NADPH
NADPH
can be used instead of NADH as electron donor, using either FAD or FMN as electron acceptor, but with an affinity 5fold or 10fold lower than NADH, respectively
additional information
-
reactive exogenous FAD substrate binds in the NADH cleft after release of NAD product. PheA2 is able to bind one FAD cofactor and one FAD substrate. PheA2 contains a dual binding cleft for NADH and FAD substrate, which alternate during catalysis. No activity with FMN, riboflavin, and NADPH
-
additional information
the flavoprotein monooxygenase uses electrons of NAD(P)H to activate and cleave a molecule of oxygen through the formation of an intermediate flavin hydroperoxide and enable the incorporation of an oxygen atom into the substrate
-
additional information
the flavoprotein monooxygenase uses electrons of NAD(P)H to activate and cleave a molecule of oxygen through the formation of an intermediate flavin hydroperoxide and enable the incorporation of an oxygen atom into the substrate
-
additional information
-
the free FAD acts as a true substrate. In addition to FAD, PheA2 is also active with FMN and riboflavin. The turnover rate of PheA2 with free flavins is strongly dependent on temperature. At 25°C, the activity with FMN and riboflavin is much higher than with FAD, but when the temperature is raised to 53°C, the turnover rates with the different flavins becomes nearly identical. Dichlorophenolindophenol is a poor cofactor
-
additional information
the free FAD acts as a true substrate. In addition to FAD, PheA2 is also active with FMN and riboflavin. The turnover rate of PheA2 with free flavins is strongly dependent on temperature. At 25°C, the activity with FMN and riboflavin is much higher than with FAD, but when the temperature is raised to 53°C, the turnover rates with the different flavins becomes nearly identical. Dichlorophenolindophenol is a poor cofactor
-
additional information
the free FAD acts as a true substrate. In addition to FAD, PheA2 is also active with FMN and riboflavin. The turnover rate of PheA2 with free flavins is strongly dependent on temperature. At 25°C, the activity with FMN and riboflavin is much higher than with FAD, but when the temperature is raised to 53°C, the turnover rates with the different flavins becomes nearly identical. Dichlorophenolindophenol is a poor cofactor
-
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METALS and IONS
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
Mg2+
Mn2+
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INHIBITOR
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
IMAGE
4-hydroxymercuribenzoate
complete inhibition at 0.02 mM
Ag+
0.02 mM completely inhibits; complete inhibition at 0.02 mM
Cu2+
0.02 mM completely inhibits; complete inhibition at 0.02 mM
FAD
with respect to the total phenol hydroxylase activity, concentrations higher than 0.01 mM inhibit the catalyzed reaction; with respect to the total phenol hydroxylase activity, concentrations higher than 0.01 mM inhibit the catalyzed reaction
Fe3+
0.1 mM inhibits by 23%, 1 mM completely inhibits; complete inhibition at 1 mM
N-ethylmaleimide
0.1 mM inhibits by 38%, 1 mM completely inhibits; complete inhibition at 1 mM
Ni2+
0.1 mM inhibits by 79%, 1 mM completely inhibits; complete inhibition at 1 mM
p-hydroxymercuribenzoate
0.0005 mM inhibits by 53%,0.02 mM completely inhibits the enzymic activity
additional information
no effect by 1 mM of iodoacetamide, phenylmethylsulfoxide, or EDTA
-
additional information
no effect by 1 mM of iodoacetamide, phenylmethylsulfoxide, or EDTA
-
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ACTIVATING COMPOUND
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
IMAGE
flavin reductase PheA2
the two-protein system phenol hydroxylase consists of an oxygenase (PheA1) and a flavin reductase (PheA2). PheA1 shows almost no phenol hydroxylase activity when assayed at 50°C and pH 7.0 in absence of PheA2. The PheA1-mediated conversion of phenol to catechol is strongly stimulated in presence of catalytic amounts of PheA2
-
phenol hydroxylase PheA2
PheA1-mediated conversion of phenol to catechol is strongly stimulated in the presence of catalytic amounts of PheA2
-
additional information
iodoacetamide, phenylmethylsulfonyl fluoride, and EDTA, at 1 mM, do not affect the activity of the pure enzyme
-
additional information
iodoacetamide, phenylmethylsulfonyl fluoride, and EDTA, at 1 mM, do not affect the activity of the pure enzyme
-
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KM VALUE [mM]
SUBSTRATE
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
IMAGE
0.0016
FAD
NADH-dependent reduction, 25°C, pH 7.0, recombinant PheA2
0.0055
FMN
NADH-dependent reduction, 25°C, pH 7.0, recombinant PheA2