Ligand citric acid

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Basic Ligand Information

Molecular Structure
Picture of citric acid (click for magnification)
Molecular Formula
BRENDA Name
InChIKey
C6H8O7
citric acid
KRKNYBCHXYNGOX-UHFFFAOYSA-N
Synonyms:
2-hydroxypropane-1,2,3-tricarboxylate, citrate, L-Citric acid, Magnesium citrate

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Roles as Enzyme Ligand

In Vivo Substrate in Enzyme-catalyzed Reactions (19 results)

EC NUMBER
PROVEN IN VIVO REACTION
REACTION DIAGRAM
LITERATURE
ENZYME 3D STRUCTURE
acetyl-CoA + citrate = acetate + (3S)-citryl-CoA
show the reaction diagram
-
ATP + citrate + CoA = ADP + phosphate + (3S)-citryl-CoA
show the reaction diagram
-
ATP + citrate + L-glutamate = ADP + phosphate + beta-citryl-L-glutamate
show the reaction diagram
-
2 ATP + citrate + N6-acetyl-N6-hydroxy-L-lysine + H2O = 2 ADP + 2 phosphate + N2-citryl-N6-acetyl-N6-hydroxy-L-lysine
show the reaction diagram
-
2 ATP + citrate + N6-acetyl-N6-hydroxy-L-lysine + H2O = 2 ADP + 2 phosphate + N2-citryl-N6-acetyl-N6-hydroxy-L-lysine
show the reaction diagram
-
ATP + citrate + L-glutamate = ADP + phosphate + N-citryl-L-glutamate
show the reaction diagram
-

In Vivo Product in Enzyme-catalyzed Reactions (12 results)

EC NUMBER
PROVEN IN VIVO REACTION
REACTION DIAGRAM
LITERATURE
ENZYME 3D STRUCTURE
acetyl-CoA + H2O + oxaloacetate = citrate + CoA
show the reaction diagram
-
-
ADP + phosphate + beta-citryl-L-glutamate = ATP + citrate + L-glutamate
show the reaction diagram
-
-

Substrate in Enzyme-catalyzed Reactions (62 results)

EC NUMBER
REACTION
REACTION DIAGRAM
LITERATURE
ENZYME 3D STRUCTURE
citric acid + NAD+ = ?
show the reaction diagram
-
citric acid + NADPH + ATP = ? + NADP+ + AMP + phosphate
show the reaction diagram
-
S-adenosyl-L-methionine + citrate = S-adenosyl-L-homocysteine + ?
show the reaction diagram
-
citrate = itaconate + CO2
show the reaction diagram
-
citrate = cis-aconitate + H2O
show the reaction diagram
-
ATP + citrate + L-glutamate = ADP + phosphate + beta-citryl-L-glutamate
show the reaction diagram
-
2 ATP + citrate + N6-acetyl-N6-hydroxy-L-lysine + H2O = 2 ADP + 2 phosphate + N2-citryl-N6-acetyl-N6-hydroxy-L-lysine
show the reaction diagram
-
ATP + N-acetyl-L-aspartate + citrate = ?
show the reaction diagram
-
ATP + citrate + L-glutamate = ADP + phosphate + N-citryl-L-glutamate
show the reaction diagram
-

Product in Enzyme-catalyzed Reactions (36 results)

EC NUMBER
REACTION
REACTION DIAGRAM
LITERATURE
ENZYME 3D STRUCTURE
Fe(III)-dicitrate + NADPH + H+ = Fe(II) + citrate + NADP+
show the reaction diagram
-
-
acetyl-CoA + H2O + oxaloacetate = 2-hydroxypropane-1,2,3-tricarboxylate + CoA
show the reaction diagram
-
-
acetyl-CoA + H2O + oxaloacetate = citrate + CoA
show the reaction diagram
-
acetyl-CoA + H2O + oxaloacetate = citrate + CoA
show the reaction diagram
-
-
acetate + oxaloacetate = citrate
show the reaction diagram
cis-aconitate + H2O = citrate
show the reaction diagram
-
-
ADP + phosphate + beta-citryl-L-glutamate = ATP + citrate + L-glutamate
show the reaction diagram
-
-

Enzyme Cofactor/Cosubstrate (3 results)

EC NUMBER
COMMENTARY
LITERATURE
ENZYME 3D STRUCTURE

Activator in Enzyme-catalyzed Reactions (114 results)

EC NUMBER
COMMENTARY
LITERATURE
ENZYME 3D STRUCTURE
30% activation
-
the enzyme is more active in presence of multivalent anions, citrate, phosphate or sulfate, in comparison to monovalent anions, e.g. acetate or chloride
-
148% relative activity at 10 mM
-
up to 50% increase in activity
-
20 mM, 140% activity
-
induced by
-
25 mM sodium citrate buffer results in 170% activity compared to 100% activity in sodium acetate buffer, both pH 5.6
-
highest stimulation at 50 mM and 30°C only for phlorizin activity
-
activates
-
enhancement of activity in absence of glycerol
-
17% activation at 120 nM, 32% activation at 1200 nM
-
enhances activity
-
activates atrazine degradation activity in vivo
-
activates
-
expression is induced by citrate
-

Inhibitor in Enzyme-catalyzed Reactions (519 results)

EC NUMBER
COMMENTARY
LITERATURE
ENZYME 3D STRUCTURE
1mM, 48.3% residual activity
-
1 mM, 24% inhibition
-
incubation of glucose-6-phosphate dehydrogenase from Leuconostoc mesenteroides with Fe2+ and citrate results in rapid O2-dependent inactivation of the enzyme. The Fe(2+)-citrate complex binds to the glucose 6-phosphate binding site and then undergoes reaction with H2O2 formed in solution leading to the oxidative modification of amino acids essential for enzyme activity
-
competitive
-
50 mM, pH 5.4, 72% inhibition
-
5 mM
-
2 mM, 28% residual activity
-
competitive
univalent anion, competitive vs. ascorbate
-
76% inhibition at 5 mM
-
competitive inhibition with respect to 2-oxoglutarate
-
30% inhibition at 5 mM
-
92 mM, pH 8, very slight inhibition
-
slight
-
inhibited by high concentrations, 40 mM
-
10 mM, 60% inhibition of oxidative deamination
-
at 6.67 mM 29% inhibition
-
in acid pH range: inhibitor of reduction of 7,8-dihydrofolate but not folate
-
1 mM, about 10% inhibition
-
2.5 mM, 25% inhibition
-
40 mM, 22% residual activity
-
to some extent
-
to some extent
-
inactivation at pH 5.5, Zn2+ protects
-
1 mM, 82% residual activity
-
activity can by restored with Mg2+
-
2.5 mM, 82% residual activity
-
65% residual activity at 10 mM
-
feedback inhibition
-
40% inhibition at 50 mM
-
0.167 M, weak
-
plasmalogen-specific PLA2
depressed activity
-
lysosomal enzyme
-
inhibits the cardiac enzyme
-
competitive
-
at 0.2 M 50% of initial activity with ssDNA
-
slight inhibition
-
24% inhibition at 6 mM
-
25 mM, 54% inhibition
-
64% inhibition at 5 mM
-
36.16% residual activity at 5 mM
-
no other organic acids, highest inhibition at low pH
-
citrate ions are shown to bind at only three well-defined sites involving both ion pairs and hydrogen bonds. Molecular dynamics simulations evidence that citrate binding has a remarkable conformational influence on the 3D structure of carnosinase, increasing the binding affinity of carnosine to the catalytic site
-
partial inhibition
-
weak
-
slight inhibitory effect
-
enzyme from mesenteric lymph nodes
-
competitive inhibition
-
40 mM, 44% inhibition
-
binding of the ligand to the active site involves stabilizing interactions, such as a carboxylate group that binds the nickel ions at the active site and several hydrogen bonds with the surrounding residues
8 mM: 95% of activity compared to H2O
-
buffer
-
6 mM
-
20% inhibition at 0.5 mM
-
9 mM
-
competitive
-
stronger inhibitory effect on strain ATCC 367 than on IOEB 9809
-
above 5.0 mM, weak
-
competitive
-
Ki: 7.5 mM
-
competitive
competitive
-
weak
-
competitive
slight
-
noncompetitive, localization of binding pocket on the enzyme outside the active site
-
not
-

Metals and Ions (1 result)

EC NUMBER
COMMENTARY
LITERATURE
ENZYME 3D STRUCTURE
bound to the steroid-binding cavity via Tyr55 and His117, involved in the induced fit mechanism
-

3D Structure of Enzyme-Ligand-Complex (PDB) (705 results)

EC NUMBER
ENZYME 3D STRUCTURE

Enzyme Kinetic Parameters

kcat Value (Turnover Number) (10 results)

EC NUMBER
TURNOVER NUMBER [1/S]
TURNOVER NUMBER MAXIMUM [1/S]
COMMENTARY
LITERATURE
5.3
-
pH 8, 25°C, Lineweaver-Burk method

KM Value (47 results)

EC NUMBER
KM VALUE [MM]
KM VALUE MAXIMUM [MM]
COMMENTARY
LITERATURE
1.24
-
pH 8.0, 30°C
0.87
-
at pH 8.0 and 37°C
1.24
-
pH 8.0, 30°C

Ki Value (41 results)

EC NUMBER
KI VALUE [MM]
KI VALUE MAXIMUM [MM]
COMMENTARY
LITERATURE
0.0205
-
-
0.4
0.5
calculated from the slopes or intercepts
8.6
-
-
60
-
-
3
-
pH 6.0
0.15
-
-
0.8
-
with respect to ADP
150
-
pH 8.0, temperature not specified in the publication
4.5
-
competitive, 30°C, pH 8.5
0.000011
-
pH 6.0, 25°C
7.5
-
-
0.0025
-
-
0.13
-
pH 8, 70°C
7.4
-
pH 8.0, 70°C
18
-
-

IC50 Value (7 results)

EC NUMBER
IC50 VALUE
IC50 VALUE MAXIMUM
COMMENTARY
LITERATURE
0.043
-
-
62.91
-
-
63
-
pH 7.5, 37°C

References & Links