Ligand L-ascorbic acid

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Basic Ligand Information

Molecular Structure
Picture of L-ascorbic acid (click for magnification)
Molecular Formula
BRENDA Name
InChIKey
C6H8O6
L-ascorbic acid
CIWBSHSKHKDKBQ-JLAZNSOCSA-N
Synonyms:
ascorbate, ascorbate[side 1], ascorbic acid, D-isoascorbic acid, L-(+)-ascorbate, L-(+)-ascorbic acid, L-ascorbate, L-ascorbate[side 1], L-xyloascorbic acid, reduced ascorbate, reduced ascorbic acid, vitamin C


Show all pahtways known for Show all BRENDA pathways known for L-ascorbic acid

Roles as Enzyme Ligand

In Vivo Substrate in Enzyme-catalyzed Reactions (38 results)

EC NUMBER
PROVEN IN VIVO REACTION
REACTION DIAGRAM
LITERATURE
ENZYME 3D STRUCTURE
L-(+)-ascorbate + ferricytochrome b5 = monodehydro-L(+)-ascorbate + ferrocytochrome b5
show the reaction diagram
-
ascorbate + H2O2 = ?
show the reaction diagram
-
protoporphyrin IX + ascorbate + O2 = hematinic acid + a tripyrrole + Fe3+
show the reaction diagram
-
amylopectin + ascorbic acid + O2 = malto-aldonic acids + dehydroascorbate
show the reaction diagram
-
[protein]-Npi-phospho-L-histidine + L-ascorbate[side 1] = [protein]-L-histidine + L-ascorbate 6-phosphate[side 2]
show the reaction diagram
-

In Vivo Product in Enzyme-catalyzed Reactions (13 results)

EC NUMBER
PROVEN IN VIVO REACTION
REACTION DIAGRAM
LITERATURE
ENZYME 3D STRUCTURE
L-galactose + NAD+ = L-ascorbate + NADH
show the reaction diagram
-
-
L-gulono-1,4-lactone + O2 = L-ascorbate + H2O2
show the reaction diagram
-
-
L-galactono-1,4-lactone + O2 = L-ascorbate + H2O2
show the reaction diagram
-
-

Substrate in Enzyme-catalyzed Reactions (398 results)

EC NUMBER
REACTION
REACTION DIAGRAM
LITERATURE
ENZYME 3D STRUCTURE
ascorbate + O2 = ?
show the reaction diagram
-
L-ascorbate + H2O2 + H+ = ?
show the reaction diagram
ascorbate + H2O2 = monodehydroascorbate + H2O
show the reaction diagram
-
ascorbate + H2O2 = dehydroascorbate + H2O
show the reaction diagram
ascorbate + H2O2 = ? + H2O
show the reaction diagram
-
ascorbate + H2O2 = ?
show the reaction diagram
-
2-oxoglutarate + O2 + ascorbate = succinate + dehydroascorbate + CO2 + H2O
show the reaction diagram
-
2-oxoglutarate + O2 + ascorbate = succinate + CO2 + dehydroascorbate + H2O
show the reaction diagram
-
protoporphyrin IX + ascorbate + O2 = hematinic acid + a tripyrrole + Fe3+
show the reaction diagram
-
L-tyrosine + ascorbate + O2 = 3,4-dihydroxy-L-phenylalanine + dehydroascorbate + H2O
show the reaction diagram
-
CMP-N-acetylneuraminate + ascorbic acid + O2 = CMP-N-glycoloylneuraminate + dehydroascorbate + H2O
show the reaction diagram
-
amylopectin + ascorbic acid + O2 = malto-aldonic acids + dehydroascorbate
show the reaction diagram
-
ascorbate + Fe2+ + O2 = ?
show the reaction diagram
-
ascorbic acid + O2 = ?
show the reaction diagram
-
NO2- + reduced ascorbate = NO + oxidized ascorbate
show the reaction diagram
-
nitric oxide + reduced ascorbate = nitrous oxide + oxidized ascorbate + H2O
show the reaction diagram
-
nitric oxide + ascorbic acid = ?
show the reaction diagram
-
sucrose + L-ascorbic acid = D-fructose + L-ascorbic acid 2-glucoside
show the reaction diagram
-
[protein]-Npi-phospho-L-histidine + L-ascorbate[side 1] = [protein]-L-histidine + L-ascorbate 6-phosphate[side 2]
show the reaction diagram
-
3'-phosphoadenylylsulfate + ascorbic acid = adenosine 3',5'-bisphosphate + ?
show the reaction diagram
-
maltose + L-ascorbic acid = L-ascorbic acid alpha-D-glucoside
show the reaction diagram
-
maltose + L-ascorbic acid = L-ascorbic acid alpha-D-glucoside
show the reaction diagram
-
ascorbic acid + H2O = ?
show the reaction diagram
-
ascorbic acid + levan = ascorbic acid 2-fructoside + ?
show the reaction diagram
-

Product in Enzyme-catalyzed Reactions (34 results)

EC NUMBER
REACTION
REACTION DIAGRAM
LITERATURE
ENZYME 3D STRUCTURE
L-galactose + NAD+ = L-ascorbate + NADH
show the reaction diagram
-
-
(R)-dopaxanthin + dehydroascorbic acid + O2 = (R)-dopaxanthin quinone + L-ascorbic acid + H2O
show the reaction diagram
-
-
2 L-ascorbate + H2O2 + 2 H+ = L-ascorbate + L-dehydroascorbate + 2 H2O
show the reaction diagram
-
(R)-dopaxanthin + dehydroascorbic acid + O2 = (R)-dopaxanthin quinone + L-ascorbic acid + H2O
show the reaction diagram
-
-
dehydroascorbate + glutathione = ascorbate + glutathione disulfide
show the reaction diagram
-
-
L-ascorbic acid-2-O-alpha-D-glucoside + H2O = L-ascorbic acid + D-glucose
show the reaction diagram
-
ascorbic acid 2-sulfate + H2O = ascorbic acid + sulfate
show the reaction diagram
-
-
ascorbate 2-sulfate + H2O = ascorbate + sulfate
show the reaction diagram
-
-

Enzyme Cofactor/Cosubstrate (74 results)

EC NUMBER
COMMENTARY
LITERATURE
ENZYME 3D STRUCTURE
requirement
-
5 mM, 10fold stimulation
-
increase of activity
-
plus NADH very low conversion and no aldosterone production, in synergism with NADH, malate and NADP+ increase of aldosterone synthetase activity in zona glomerulosa, not zona fasciculate
-
required
-
required
-
activation, especially together with optimal NADH
-
at 5 mM, stimulation of 42%
-
cofactor system composed of Fe2+, cysteine and/or ascorbate functions under aerobic and anaerobic conditions, a second cofactor system with NADH/FMN requires anaerobic conditions
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Activator in Enzyme-catalyzed Reactions (242 results)

EC NUMBER
COMMENTARY
LITERATURE
ENZYME 3D STRUCTURE
prevents oxidation of substrates
-
5 mM, enhances activity 2-hydroxy-2-ethyl-3-oxobutanoate as substrate
-
17.5-26% activation at 1 mM
-
treatment with excess ascorbate at pH 4.85 to pH 5.5 in the presence of citrate and chloride and in the absence of O2, 9fold increase in maximal velocity
-
enhances total turnover number compared to reaction without antioxidant
-
addition of 2.5 mM ascorbate to the standard assay results in an 20% increase in the PDO-specific activity
-
incubation of the purified enzyme (PheB) with Fe2+ and ascorbate increases its activity by approximately sevenfold
-
protects against autooxidation
-
required
-
2 mM, no further stimulation above 2 mM
-
2 m ascorbate is used in assay conditions
-
slightly reduced in the absence of ascorbate
-
slightly reduced activity in the absence of ascorbate
-
ascorbic acid is not necessarily required for the reaction, however, in the presence of ascorbic acid, the reaction rate is greatly stimulated
-
required
-
1 mM activates
-
required for full activity
-
activation
-
stimulates NOD activity, reduces the oxidized Cygb-NOD intermediate with a second order rate of 1000 M/s, Km is 0.25 mM
-
prevents degradation of tetrapyrroles by reactive oxygen species
-
0.1 mM, stimulates
-
complete dependance on added ascorbate, e.g. isoascorbate, glucoascorbate, D-ascorbate
-
activation of tyrosine hydroxylase activity
-
activates
-
activity with the natural substrate (3S,5S)-carbapenam-3-carboxylate in absence of ascorbate is 2% compared to the activity in presence of ascorbate. Ascorbate does not stimulate turnover of the (3S,5R)- or (3R,5R)-stereoisomers
-
required for full activity, can not be replaced as a reductant by 2-mercaptoethanol or dithiothreitol
-
required for enzyme stability
-
provides a nearly 100fold increase in enzyme activity
-
in absence of thiols or ascorbate, no NO generation is detected from xanthine oxidase mediated organic nitrate reduction
-
required
-
addition of ascorbic acid to a reconstituted system composed of nitrite reductase and ferredoxin proteins leads to reduction of nitrite at a rate nearly equal to that is obtainable with the NADPH/ferredoxin-NADPH-reductase/ferredoxin-nitrite reductase system
-
can replace 2-mercaptoethanol, best reducing agent for reaction assay
-
at 0.5 mM, 50% activation
-
at 5 mM, stimulation of 42%
-
10 mM, slightly activates
-
activation
-
124.4% activity at 1 mM
-
maximal activation at 1 mM
-
increases PHOSPHO1 expression in matrix vesicles after 12 days in culture
-
activates
-
2 mM, slight activation, cellulase I
-
1.6fold stimulation only for phlorizin activity
-
128.23% activity at 100 mM
-
about 110% activity at 5 mM
-
1 mM, 107% of initial activity
-
reducing agents in optimal concentrations of 20 mM or above are a prerequisite for high CO2 fixation turnovers, with dithiothreitol enhancing the carboxylation 16.2fold compared with a control without reducing agent, followed by ascorbate (15.5fold), Na2S2O5 (13.6fold) and 2-mercaptoethanol (7.2fold)
-
strongly stimutates
-
up to 3fold activation
-
activation by 2-mercaptoethanol, EDTA, and ascorbic acid. The effects of EDTA and ascorbic acid are additive
-
enhances slightly glyoxalase I activity, dose-dependently 0-2 g/l, pH 6.6, 37C
-
optimum activity at 6 mM ascorbate
-
enzyme activity depends on the presence of a reducing compound to a final concentration of 0.1mM
-
required, D-ascorbate shows 80% of L-ascorbate in enhancing the reaction, cannot be replaced by other reducing agents
-

Inhibitor in Enzyme-catalyzed Reactions (205 results)

EC NUMBER
COMMENTARY
LITERATURE
ENZYME 3D STRUCTURE
1mM, 14% residual activity
-
in 100 mM MES buffer (pH 6.5) with 200 mM NADPH, 0.25 mM decanal, and 125 microg of FALDR fusion protein. 1 mM inhibits by 24%
-
30% inhibition at 1 mM
-
at concentrations normally found in tissue. It is proposed that ascorbate facilitates the storage of glycogen in muscle at rest by inhibiting glycolysis. Aldolase and muscle G-actin protect and reverse inhibition
-
inhibits both the reductase and dehydrogenase reactions by 30% at 1 mM
-
1 mM, 41% inhibition, linear-competitive inhibition, inhibition is reversible, equilibrium-type of feedback regulation for L-ascorbate synthesis; reversible inhibition by the end-product of the biosynthetic pathway
-
0.025 mM FeCl3 and 0.035 mM ascorbate causes a 90% enzyme inactivation after 120 min = inactivation of metal-catalyzed oxidation; several amino-acids prevent the inactivation; under aerobic conditions 0.025 mM FeCl3 causes a 50% enzyme inactivation after 120 min
-
10% inhibition at 1 mM, 95% inhibition at 10 mM
-
high concentration supresses liver enzyme activity
-
58% inhibition at 0.1 mM
-
31.2% inhibition at 0.1 mM
-
poising the enzyme in the active state using sodium L-ascorbate, allows for capturing a highly active state that turns over peroxide in a high potential regime
in vitro inhibitor
-
noncompetitive inhibition of the LOX/4-nitroso-N,N-dimethylaniline reaction
-
30% inhibition at 1 mM
-
completely inhibits at concentrations over 25 mM
-
1 mM, 20% inhibition
-
inactivation due to release of peroxide from reaction of ascorbate and O2 in absence of proclavaminate, but in presence of Fe2+, t1/2: 50 min, catalase protects
-
5 mM, 70% inhibition
-
ascorbate causes a time-dependent inhibition of L-proline hydroxylation. The addition of ascorbate does not stimulate L-proline-coupled turnover of 2-oxoglutarate, but does stimulate L-proline-uncoupled turnover
-
slight
-
52% inhibition at 50 mM
-
2.0 mM
-
without NADH, inhibition of aldosterone synthetase
-
2 mM, 78% inhibition
-
above 0.4 mM for the purified enzyme, above 1.5 mM for the enzyme in crude extract
-
required in vitro, inhibitory in vivo
-
inhibitory at high concentrations
-
5 mM, 44% inhibition
-
inhibits the purified enzyme in vitro, and the formation of cross-linked collagen
-
moderate inhibition
-
1 mM, 81% inhibition
-
1 mM, 45% inhibition
-
18.3% inhibition at 1 mM
-
2 mM, 25% inhibition
-
inhibition by ascorbate is PFK-1 concentration dependent. Ascorbate does not inhibit above 200 nM PFK-1. It is concluded that ascorbate inhibits PFK-1 dimers (and perhaps monomers) but not PFK-1 tetramers
-
72% inhibition at 0.5 mM
-
treatment of rabbit muscle pyruvate kinase with 10 mM ascorbate causes an inactivation with the cleavage of peptide bond. The inactivation or fragmentation of the enzyme is prevented by addition of Mg2+, catalase, and mannitol, but ADP and PEP the substrates do not show any effect
-
inhibition is dependent on concentration of PFK-1. No inhibition above 200 nM PFK-1. It is concluded that ascorbate inhibits PFK-1 dimer (and perhaps monomers) but not PFK-1 tetramers
-
1 mM, 40% residual activity
-
0.5 mM inhibits by ca. 19%. Ascorbate/Cu2+ (0.5 mM/0.001 mM) system shows ca. 91% inactivation
-
ascorbate/Cu2+ system is the most potent in inactivating the lactonase activity (by 90%). Cu2+ remarkably enhances the inactivation in the presence of ascorbate. Ascorbate/Cu2+ (0.5 mM/0.001 mM) system shows ca. 95% inactivation. Ascorbate/Cu2+-mediated inactivation of lactonase activity is prevented by catalase (90%), oleic acid (73% at 0.01 mM) and dioleoylphosphatidylcholine (68% at 0.1 mM). Ascorbate/Fe2+ (0.5 mM/0.002 mM) system shows 20% inactivation
-
10 mM, 2.5% loss of activity
-
endogenous inhibitor, inhibits the phosphodiesterase activity of the enzyme through reduction of Cu2+
-
inactivation of the purified enzyme by incubation at 37C, enhancing by addition of Cu2+, Fe2+ and Fe3+
-
inhibition of cytosolic enzyme
-
slight inhibition
-
oxidative inactivation of the Zn2+ -enzyme
-
0.5 mM inhibits by ca. 22%. Ascorbate/Cu2+ (0.5 mM/0.001 mM) system shows ca. 63% inactivation
-
28.4% inhibition at 5 mM, 34.9% at 10 mM
-
Ki: 2 mM
-
competitive
-
only in presence of Cu2+
-
inhibits AA-NADase on both NADase and ADPase activities through the reduction of Cu(II) in AA-NADase to Cu(I)
-
strong
-
21.8% inhibition at 5 mM
-
19% inhibition at 1 mM
-
in an unbuffered system L-ascorbic acid inactivates urease in a biphasic manner by denaturation brought about by ascorbic acid-lowered pH. In a buffered system neither ascorbic acid nor dehydroascorbic acid themselves are inhibitors of urease
-
50% inhibition at 10 mM
-
68% residual activity at 1 mM
-
8% inhibition at 16 mM
-
decreases enzyme activity in lung carcinoma NCI-H82 cells and reduces the cell viability, overview
-
activity stimulated by NADH and FMN (anaerobic) is inhibited by 40%
-
enzyme is inhibited by an ascorbate plus Fe2+ system under aerobic conditions,16% residual activity at 2 mM ascorbate/0.02 mM Fe2+. Inactivation requires hydrogen peroxide, and can be prevented by catalase, EDTA, Mg2+, isocitrate, 20 mM glutathione, 20 mM dithiothreitol or 40 mM L-cysteine
-
0.4 mM, 23% inhibition
-
54.6% inhibition at 1 mM
-
48% loss of activity at 0.1 mM, complete inactivation at 1.0 mM
-
1 mM, 15% inhibition
-
1 mM, 77% residual activity
-
little loss of activity with 2 mM ascorbate alone. Complete inactivation by co-incubation with 1 mM H2O2, 0.002 mM Fe3+, 2 mM ascorbate for 30 min
-

Metals and Ions (2 results)

EC NUMBER
COMMENTARY
LITERATURE
ENZYME 3D STRUCTURE
activates at 0.5 mM
-
activates at low concentrations
-

3D Structure of Enzyme-Ligand-Complex (PDB) (21 results)

Enzyme Kinetic Parameters

kcat Value (Turnover Number) (52 results)

EC NUMBER
TURNOVER NUMBER [1/S]
TURNOVER NUMBER MAXIMUM [1/S]
COMMENTARY
LITERATURE
520
-
pH 5.0, 23C
0.2
-
in 50 mM MOPS, pH 7.0, at 29C
0.97
-
-

KM Value (147 results)

EC NUMBER
KM VALUE [MM]
KM VALUE MAXIMUM [MM]
COMMENTARY
LITERATURE
12
-
-
0.192
-
-
0.13
-
pH 5.0, 23C
0.2
-
-
0.28
-
+ 0.02 mM N-dansyl-Tyr-Phe-Gly
0.0052
-
-
0.009
-
at pH 7.0 and 37C

Ki Value (26 results)

EC NUMBER
KI VALUE [MM]
KI VALUE MAXIMUM [MM]
COMMENTARY
LITERATURE
0.027
-
promethazine oxidation
10
-
-

IC50 Value (22 results)

EC NUMBER
IC50 VALUE
IC50 VALUE MAXIMUM
COMMENTARY
LITERATURE
0.45
-
-
2.87
-
holo-enzyme containing Cu2+ and Zn2+, pH 7.4, 37C
1.79
-
pH 7.4, 37C, inhibition of the NADase activity
0.141
-
recombinant enzyme

References & Links