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Enzyme Nomenclature
Information on EC 1.14.13.242 - 3-hydroxy-2-methylpyridine-5-carboxylate monooxygenase
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EC Tree
1.14.13.242 3-hydroxy-2-methylpyridine-5-carboxylate monooxygenaseIUBMB Comments
Contains FAD. The enzyme, characterized from the bacteria Pseudomonas sp. MA-1 and Mesorhizobium loti, participates in the degradation of pyridoxine (vitamin B6). Although the enzyme was initially thought to be a dioxygenase, oxygen-tracer experiments have shown that it is a monooxygenase, incorporating only one oxygen atom from molecular oxygen. The second oxygen atom that is incorporated into the product originates from a water molecule, which is regenerated during the reaction and thus does not show up in the reaction equation.
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Word Map
- 1.14.13.242
- flavin
- flavoproteins
- fad
- hydroxylases
-
mesorhizobium
-
flavoenzyme
-
electrophilic
- loti
-
acyclic
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flavin-dependent
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ring-cleavage
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hydride
- isoalloxazine
The expected taxonomic range for this enzyme is: Bacteria, Eukaryota
Reaction Schemes
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SYNONYM 
ORGANISM
UNIPROT
COMMENTARY 
LITERATURE
2-methyl-3-hydroxypyridine 5-carboxylic acid dioxygenase
-
-
-
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2-methyl-3-hydroxypyridine 5-carboxylic acid oxygenase
2-methyl-3-hydroxypyridine-5-carboxylic acid oxygenase
3-hydroxy-2-methylpyridine carboxylate dioxygenase
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3-hydroxy-2-methylpyridinecarboxylate dioxygenase
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misleading
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EC 1.14.12.4
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formerly
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methylhydroxypyridine carboxylate dioxygenase
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methylhydroxypyridinecarboxylate oxidase
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MHPCO
mlr6788
2-methyl-3-hydroxypyridine-5-carboxylic acid oxygenase
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REACTION
REACTION DIAGRAM
COMMENTARY
ORGANISM
UNIPROT
LITERATURE
3-hydroxy-2-methylpyridine-5-carboxylate + NAD(P)H + H+ + O2 = 2-(acetamidomethylidene)succinate + NAD(P)+
3-hydroxy-2-methylpyridine-5-carboxylate + NAD(P)H + H+ + O2 = 2-(acetamidomethylidene)succinate + NAD(P)+
reaction proceeds in a concerted fashion via a ternary complex of oxygenase, NADH and 3-hydroxy-2-methylpyridine-5-carboxylate
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3-hydroxy-2-methylpyridine-5-carboxylate + NAD(P)H + H+ + O2 = 2-(acetamidomethylidene)succinate + NAD(P)+
ordered mechanism in which 3-hydroxy-2-methylpyridine-5-carboxylate binds first, followed by NADH. The first product NAD+ is then released, followed by oxygen binding and finally release of the oxygenated and reduced cleavage product 2-(acetamidomethylene)succinate
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3-hydroxy-2-methylpyridine-5-carboxylate + NAD(P)H + H+ + O2 = 2-(acetamidomethylidene)succinate + NAD(P)+
the enzyme catalyzes both a classical hydroxylation and a subsequent unique hydrolysis of the hydroxylated substrate to yield the acyclic product
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3-hydroxy-2-methylpyridine-5-carboxylate + NAD(P)H + H+ + O2 = 2-(acetamidomethylidene)succinate + NAD(P)+
the binding proceeds in two steps: an enzyme-substrate complex initially formed is followed by a ligand-induced isomerization
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3-hydroxy-2-methylpyridine-5-carboxylate + NAD(P)H + H+ + O2 = 2-(acetamidomethylidene)succinate + NAD(P)+
oxygenation reaction occurs via an electrophilic aromatic substitution mechanism
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3-hydroxy-2-methylpyridine-5-carboxylate + NAD(P)H + H+ + O2 = 2-(acetamidomethylidene)succinate + NAD(P)+
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REACTION TYPE
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
oxidation
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redox reaction
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reduction
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-
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-
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PATHWAY SOURCE
PATHWAYS
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SYSTEMATIC NAME
IUBMB Comments
3-hydroxy-2-methylpyridine-5-carboxylate,NAD(P)H:oxygen oxidoreductase (ring-opening)
Contains FAD. The enzyme, characterized from the bacteria Pseudomonas sp. MA-1 and Mesorhizobium loti, participates in the degradation of pyridoxine (vitamin B6). Although the enzyme was initially thought to be a dioxygenase, oxygen-tracer experiments have shown that it is a monooxygenase, incorporating only one oxygen atom from molecular oxygen. The second oxygen atom that is incorporated into the product originates from a water molecule, which is regenerated during the reaction and thus does not show up in the reaction equation.
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CAS REGISTRY NUMBER
COMMENTARY
37256-69-2
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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
2-methyl-3-hydroxypyridine-5-carboxylic acid + NADH + O2 + H+
2-(acetamidomethylene)succinate + NAD+
-
-
-
?
3-hydroxy-2-methylpyridine-5-carboxylate + NAD(P)H + H+ + O2
2-(acetamidomethylene)succinate + NAD(P)+
-
-
-
-
?
3-hydroxy-2-methylpyridine-5-carboxylate + NAD(P)H + H+ + O2
2-(acetamidomethylidene)succinate + NAD(P)+
3-hydroxy-2-methylpyridine-5-carboxylate + NADH + H+ + O2
2-(acetamidomethylene)succinate + NAD+
3-hydroxy-2-methylpyridine-5-carboxylate + NADH + H+ + O2
2-(acetamidomethylene)succinate + NAD+ + H2O
3-hydroxy-2-methylpyridine-5-carboxylate + NADH + O2
2-(acetamidomethylene)succinate + NAD(P)+
3-hydroxy-2-methylpyridine-5-carboxylate + NADH + O2
2-(acetamidomethylene)succinate + NAD+
3-hydroxy-2-methylpyridine-5-carboxylate + NADH + O2 + H+
2-(acetamidomethylene)succinate + NAD+
3-hydroxy-2-methylpyridine-5-carboxylate + NADPH + H+ + O2
2-(acetamidomethylene)succinate + NADP+
-
-
-
-
?
5-hydroxynicotinic acid + NADH + H+ + O2
alpha-(N-formylaminomethylene)succinic acid + NAD+ + H2O
5-pyridoxic acid + NADH + H+ + O2
alpha-(N-acetylaminomethylene)-beta-hydroxymethyl succinic acid + NAD+ + H2O
5-pyridoxic acid + NADH + O2 + H+
2-(acetamidomethylene)-beta-hydroxymethyl succinate + NAD+
5% of the activity with 2-methyl-3-hydroxypyridine-5-carboxylic acid
-
-
?
3-hydroxy-2-methylpyridine-5-carboxylate + NAD(P)H + H+ + O2
2-(acetamidomethylidene)succinate + NAD(P)+
-
-
-
?
3-hydroxy-2-methylpyridine-5-carboxylate + NAD(P)H + H+ + O2
2-(acetamidomethylidene)succinate + NAD(P)+
-
-
-
?
3-hydroxy-2-methylpyridine-5-carboxylate + NAD(P)H + H+ + O2
2-(acetamidomethylidene)succinate + NAD(P)+
-
-
-
?
3-hydroxy-2-methylpyridine-5-carboxylate + NADH + H+ + O2
2-(acetamidomethylene)succinate + NAD+
-
-
-
?
3-hydroxy-2-methylpyridine-5-carboxylate + NADH + H+ + O2
2-(acetamidomethylene)succinate + NAD+
-
-
-
?
3-hydroxy-2-methylpyridine-5-carboxylate + NADH + H+ + O2
2-(acetamidomethylene)succinate + NAD+
-
-
-
?
3-hydroxy-2-methylpyridine-5-carboxylate + NADH + H+ + O2
2-(acetamidomethylene)succinate + NAD+ + H2O
-
-
-
?
3-hydroxy-2-methylpyridine-5-carboxylate + NADH + H+ + O2
2-(acetamidomethylene)succinate + NAD+ + H2O
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-
-
?
3-hydroxy-2-methylpyridine-5-carboxylate + NADH + H+ + O2
2-(acetamidomethylene)succinate + NAD+ + H2O
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-
-
?
3-hydroxy-2-methylpyridine-5-carboxylate + NADH + O2
2-(acetamidomethylene)succinate + NAD(P)+
-
-
-
?
3-hydroxy-2-methylpyridine-5-carboxylate + NADH + O2
2-(acetamidomethylene)succinate + NAD(P)+
-
-
-
?
3-hydroxy-2-methylpyridine-5-carboxylate + NADH + O2
2-(acetamidomethylene)succinate + NAD(P)+
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-
-
?
3-hydroxy-2-methylpyridine-5-carboxylate + NADH + O2
2-(acetamidomethylene)succinate + NAD(P)+
-
-
-
-
?
3-hydroxy-2-methylpyridine-5-carboxylate + NADH + O2
2-(acetamidomethylene)succinate + NAD(P)+
-
-
-
?
3-hydroxy-2-methylpyridine-5-carboxylate + NADH + O2
2-(acetamidomethylene)succinate + NAD(P)+
-
the nitrogen atom of the 3-hydroxy-2-methylpyridine-5-carboxylate is invariably protonated during the catalytic reaction
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-
?
3-hydroxy-2-methylpyridine-5-carboxylate + NADH + O2
2-(acetamidomethylene)succinate + NAD+
-
inducible enzyme opens the pyridine ring during the metabolic degradation of vitamin B6
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-
?
3-hydroxy-2-methylpyridine-5-carboxylate + NADH + O2
2-(acetamidomethylene)succinate + NAD+
-
enzyme is involved in degradation of vitamin B6
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-
?
3-hydroxy-2-methylpyridine-5-carboxylate + NADH + O2 + H+
2-(acetamidomethylene)succinate + NAD+
-
-
-
?
3-hydroxy-2-methylpyridine-5-carboxylate + NADH + O2 + H+
2-(acetamidomethylene)succinate + NAD+
-
-
-
?
5-hydroxynicotinic acid + NADH + H+ + O2
alpha-(N-formylaminomethylene)succinic acid + NAD+ + H2O
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-
-
?
5-hydroxynicotinic acid + NADH + H+ + O2
alpha-(N-formylaminomethylene)succinic acid + NAD+ + H2O
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-
-
?
5-hydroxynicotinic acid + NADH + H+ + O2
alpha-(N-formylaminomethylene)succinic acid + NAD+ + H2O
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-
-
?
5-hydroxynicotinic acid + NADH + O2 + H+
2-(formylamidomethylene)succinate + NAD+
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-
-
?
5-hydroxynicotinic acid + NADH + O2 + H+
2-(formylamidomethylene)succinate + NAD+
about 100% of the activity with 2-methyl-3-hydroxypyridine-5-carboxylic acid
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-
?
5-hydroxynicotinic acid + NADH + O2 + H+
2-(formylamidomethylene)succinate + NAD+
-
-
-
?
5-pyridoxic acid + NADH + H+ + O2
alpha-(N-acetylaminomethylene)-beta-hydroxymethyl succinic acid + NAD+ + H2O
5% activity compared to 3-hydroxy-2-methylpyridine-5-carboxylate
-
-
?
5-pyridoxic acid + NADH + H+ + O2
alpha-(N-acetylaminomethylene)-beta-hydroxymethyl succinic acid + NAD+ + H2O
5% activity compared to 3-hydroxy-2-methylpyridine-5-carboxylate
-
-
?
5-pyridoxic acid + NADH + H+ + O2
alpha-(N-acetylaminomethylene)-beta-hydroxymethyl succinic acid + NAD+ + H2O
5% activity compared to 3-hydroxy-2-methylpyridine-5-carboxylate
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-
?
additional information
?
-
comparisons of substrate binding structure analysis mechanism
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-
additional information
?
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comparisons of substrate binding structure analysis mechanism
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-
-
additional information
?
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comparisons of substrate binding structure analysis mechanism
-
-
-
additional information
?
-
comparisons of substrate binding structure analysis mechanism
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-
-
additional information
?
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also catalyzes the NADH oxidation reaction uncoupled with ring opening in the absence of 2-methyl-3-hydroxypyridine-5-carboxylic acid
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-
?
additional information
?
-
-
also catalyzes the NADH oxidation reaction uncoupled with ring opening in the absence of 2-methyl-3-hydroxypyridine-5-carboxylic acid
-
-
?
additional information
?
-
also catalyzes the NADH oxidation reaction uncoupled with ring opening in the absence of 2-methyl-3-hydroxypyridine-5-carboxylic acid
-
-
?
additional information
?
-
also catalyzes the NADH oxidation reaction uncoupled with ring opening in the absence of 2-methyl-3-hydroxypyridine-5-carboxylic acid
-
-
?
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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
2-methyl-3-hydroxypyridine-5-carboxylic acid + NADH + O2 + H+
2-(acetamidomethylene)succinate + NAD+
-
-
-
?
3-hydroxy-2-methylpyridine-5-carboxylate + NAD(P)H + H+ + O2
2-(acetamidomethylidene)succinate + NAD(P)+
3-hydroxy-2-methylpyridine-5-carboxylate + NADH + H+ + O2
2-(acetamidomethylene)succinate + NAD+
3-hydroxy-2-methylpyridine-5-carboxylate + NADH + O2
2-(acetamidomethylene)succinate + NAD+
3-hydroxy-2-methylpyridine-5-carboxylate + NADPH + H+ + O2
2-(acetamidomethylene)succinate + NADP+
-
-
-
-
?
5-hydroxynicotinic acid + NADH + O2 + H+
2-(formylamidomethylene)succinate + NAD+
about 100% of the activity with 2-methyl-3-hydroxypyridine-5-carboxylic acid
-
-
?
5-pyridoxic acid + NADH + O2 + H+
2-(acetamidomethylene)-beta-hydroxymethyl succinate + NAD+
5% of the activity with 2-methyl-3-hydroxypyridine-5-carboxylic acid
-
-
?
3-hydroxy-2-methylpyridine-5-carboxylate + NAD(P)H + H+ + O2
2-(acetamidomethylidene)succinate + NAD(P)+
-
-
-
?
3-hydroxy-2-methylpyridine-5-carboxylate + NAD(P)H + H+ + O2
2-(acetamidomethylidene)succinate + NAD(P)+
-
-
-
?
3-hydroxy-2-methylpyridine-5-carboxylate + NAD(P)H + H+ + O2
2-(acetamidomethylidene)succinate + NAD(P)+
-
-
-
?
3-hydroxy-2-methylpyridine-5-carboxylate + NADH + H+ + O2
2-(acetamidomethylene)succinate + NAD+
-
-
-
?
3-hydroxy-2-methylpyridine-5-carboxylate + NADH + H+ + O2
2-(acetamidomethylene)succinate + NAD+
-
-
-
?
3-hydroxy-2-methylpyridine-5-carboxylate + NADH + H+ + O2
2-(acetamidomethylene)succinate + NAD+
-
-
-
?
3-hydroxy-2-methylpyridine-5-carboxylate + NADH + O2
2-(acetamidomethylene)succinate + NAD+
-
inducible enzyme opens the pyridine ring during the metabolic degradation of vitamin B6
-
-
?
3-hydroxy-2-methylpyridine-5-carboxylate + NADH + O2
2-(acetamidomethylene)succinate + NAD+
-
enzyme is involved in degradation of vitamin B6
-
-
?
additional information
?
-
also catalyzes the NADH oxidation reaction uncoupled with ring opening in the absence of 2-methyl-3-hydroxypyridine-5-carboxylic acid
-
-
?
additional information
?
-
-
also catalyzes the NADH oxidation reaction uncoupled with ring opening in the absence of 2-methyl-3-hydroxypyridine-5-carboxylic acid
-
-
?
additional information
?
-
also catalyzes the NADH oxidation reaction uncoupled with ring opening in the absence of 2-methyl-3-hydroxypyridine-5-carboxylic acid
-
-
?
additional information
?
-
also catalyzes the NADH oxidation reaction uncoupled with ring opening in the absence of 2-methyl-3-hydroxypyridine-5-carboxylic acid
-
-
?
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COFACTOR
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
IMAGE
FAD
Km value 624 nM, one mol of the enzyme contains 1.93 mol of FAD
NADH
-
interacts with the holoenzyme in a slow catalytically irrelevant manner
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METALS and IONS
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
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INHIBITOR
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
IMAGE
6-methylnicotinic acid
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competitive with 3-hydroxy-2-methylpyridine-5-carboxylate
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DISEASE
TITLE OF PUBLICATION
LINK TO PUBMED
Infections
Molecular cloning, identification and characterization of 2-methyl-3-hydroxypyridine-5-carboxylic-acid-dioxygenase-coding gene from the nitrogen-fixing symbiotic bacterium Mesorhizobium loti.
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KM VALUE [mM]
SUBSTRATE
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
IMAGE
0.045
5-hydroxynicotinic acid
mutant enzyme Y270A, at pH 8.0 and 25°C
0.21
5-hydroxynicotinic acid
mutant enzyme Y270F, at pH 8.0 and 25°C
0.00056
N-methyl-5-hydroxynicotinic acid
-
calculation from stopped-flow data
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TURNOVER NUMBER [1/s]
SUBSTRATE
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
IMAGE
0.05
5-hydroxynicotinic acid
mutant enzyme Y270A, at pH 8.0 and 25°C
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kcat/KM VALUE [1/mMs-1]
SUBSTRATE
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
IMAGE
1.1
5-hydroxynicotinic acid
mutant enzyme Y270A, at pH 8.0 and 25°C
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Ki VALUE [mM]
INHIBITOR
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
IMAGE
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IC50 VALUE [mM]
INHIBITOR
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
IMAGE
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SPECIFIC ACTIVITY [µmol/min/mg]
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
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pH OPTIMUM
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
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TEMPERATURE OPTIMUM
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
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TEMPERATURE RANGE
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
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ORGANISM
COMMENTARY
LITERATURE
UNIPROT
SEQUENCE DB
SOURCE
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GENERAL INFORMATION
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
physiological function
additional information
physiological function
conversion of 2-methyl-3-hydroxypyridine-5-carboxylic acid to alpha-(N-acetylaminomethylene)succinic acid is the essential ring-opening step in the bacterial degradation of vitamin B6. The rearomatisation of the hydroxylated intermediate occurs spontaneously in aqueous solution. This implies that the ring-opening process occurs inside the enzyme's active site. Proposal of two pathways with reasonable energy barriers
physiological function
MHPCO is essential for the assimilation of pyridoxine, but not for its growth in a nutrient-rich medium. MHPCO is dispensable for at least nodule formation on roots of seedlings in symbiosis
physiological function
2-methyl-3-hydroxypyridine-5-carboxylic acid oxygenase (MHPCO) is a flavoenzyme that catalyzes oxidative ring opening of 2-methyl-3-hydroxypyridine-5-carboxylic acid
physiological function
-
2-methyl-3-hydroxypyridine-5-carboxylic acid oxygenase (MHPCO) is a flavoenzyme that catalyzes oxidative ring opening of 2-methyl-3-hydroxypyridine-5-carboxylic acid
-
physiological function
-
2-methyl-3-hydroxypyridine-5-carboxylic acid oxygenase (MHPCO) is a flavoenzyme that catalyzes oxidative ring opening of 2-methyl-3-hydroxypyridine-5-carboxylic acid
-
physiological function
-
conversion of 2-methyl-3-hydroxypyridine-5-carboxylic acid to alpha-(N-acetylaminomethylene)succinic acid is the essential ring-opening step in the bacterial degradation of vitamin B6. The rearomatisation of the hydroxylated intermediate occurs spontaneously in aqueous solution. This implies that the ring-opening process occurs inside the enzyme's active site. Proposal of two pathways with reasonable energy barriers
-
physiological function
-
MHPCO is essential for the assimilation of pyridoxine, but not for its growth in a nutrient-rich medium. MHPCO is dispensable for at least nodule formation on roots of seedlings in symbiosis
-
additional information
sequence comparisons, three-dimensional enzyme structure analysis, and structure comparisons with 2-hydroxybiphenyl 3-monooxygenase (HbpA) from Pseudomonas nitroreducens and 2-methyl-3-hydroxypyridine-5-carboxylic acid oxygenase (MHPCO, PDB ID 5hxi) from Mesorhizobium japonicum, overview. Despite having only 14% similarity in their primary sequences, pairwise structure alignments of PobA from Pseudomonas putida with HbpA from Pseudomonas nitroreducens and MHPCO from Mesorhizobium japonicum reveal local similarities between these structures. Key residues in the FAD-binding and substrate-binding sites of PobA are highly conserved spatially across the proteins from all three species. The PobA from Pseudomonas putida is structurally very similar to PobA from Pseudomonas fluorescens and from Pseudomonas aeruginosa. Key secondary-structure elements important for catalysis, such as the betaalphabeta fold, beta-sheet wall and alpha12 helix, are conserved across this expanded class of oxygenases
additional information
-
sequence comparisons, three-dimensional enzyme structure analysis, and structure comparisons with 2-hydroxybiphenyl 3-monooxygenase (HbpA) from Pseudomonas nitroreducens and 2-methyl-3-hydroxypyridine-5-carboxylic acid oxygenase (MHPCO, PDB ID 5hxi) from Mesorhizobium japonicum, overview. Despite having only 14% similarity in their primary sequences, pairwise structure alignments of PobA from Pseudomonas putida with HbpA from Pseudomonas nitroreducens and MHPCO from Mesorhizobium japonicum reveal local similarities between these structures. Key residues in the