Escherichia coli K-12 substr. MG1655 Reaction:

Superclasses: Reactions Classified By Conversion TypeSimple ReactionsChemical Reactions
Reactions Classified By SubstrateSmall-Molecule Reactions

EC Number:,

Enzymes and Genes:
2-methylcitrate synthaseInferred from experiment: prpC
citrate synthaseInferred from experiment: gltA

In Pathway: glyoxylate cycle, TCA cycle I (prokaryotic), mixed acid fermentation

Supersedes EC number:

The direction shown, i.e. which substrates are on the left and right sides, is in accordance with the direction in which it was curated.

Most BioCyc compounds have been protonated to a reference pH value of 7.3. Please see the PGDB Concepts Guide for more information.

Mass balance status: Balanced.

Enzyme Commission Primary Name for citrate (Si)-synthase

Enzyme Commission Synonyms for (R)-citric synthase, citrate oxaloacetate-lyase [(pro-3S)-CH2COO-->acetyl-CoA]

Enzyme Commission Primary Name for citrate synthase (unknown stereospecificity)

Enzyme Commission Synonyms for citrate condensing enzyme, CoA-acetylating citrate oxaloacetate-lyase, citrate synthetase, citric synthase, citric-condensing enzyme, citrogenase, condensing enzyme, oxaloacetate transacetase, oxalacetic transacetase

First reaction of TCA cycle; condensation of 4 carbon + 2 carbon = 6 carbon cmpd; the only step in the cycle forming a C-C bond. Acetyl CoA for the reaction is derived from either glycolysis, β-oxidation of fatty acids, or degradation of amino acids. SUBREACTION-LIST: 1. generation of a carbanion on AcCoA by base extraction of proton 2. nucleophilic attack of the carbanion AcCoA to produce citryl-CoA 3. hydrolysis of citryl-CoA = citrate + CoA

The EC number for this reaction has been modified from to in 2002.

Enzyme Commission Summary for
The stereospecificity of this enzyme is opposite to that of EC, citrate (Re)-synthase, which is found in some anaerobes. Citrate synthases for which the stereospecificity with respect to C2 of oxaloacetate has not been established are included in EC, citrate synthase (unknown stereospecificity).

Enzyme Commission Summary for
This entry has been included to accommodate those citrate synthases for which the stereospecificity with respect to C2 of oxaloacetate has not been established [cf. EC, citrate (Si)-synthase and EC, citrate (Re)-synthase.

Citations: [Lenz71, vanRooyen94, LohleinWerhahn88, Krebs80, Karpusas90, Kurz95, Sievers97, Belova97, Lee97g, Maurus03]

Gene-Reaction Schematic

Gene-Reaction Schematic

Relationship Links: BRENDA:EC:, BRENDA:EC:, ENZYME:EC:, ENZYME:EC:, IUBMB-ExplorEnz:EC:, IUBMB-ExplorEnz:EC:


Belova97: Belova LL, Sokolov AP, Morgunov IG, Trotsenko YuA (1997). "Purification and characterization of citrate synthase from Methylobacterium extorquens--a methylotrophic producer of polyhydroxybutyrate." Biochemistry (Mosc) 62(1);71-6. PMID: 9113733

Karpusas90: Karpusas M, Branchaud B, Remington SJ (1990). "Proposed mechanism for the condensation reaction of citrate synthase: 1.9-A structure of the ternary complex with oxaloacetate and carboxymethyl coenzyme A." Biochemistry 29(9);2213-9. PMID: 2337600

Krebs80: Krebs HA, Johnson WA (1980). "The role of citric acid in intermediate metabolism in animal tissues." FEBS Lett 117 Suppl;K1-10. PMID: 6998725

Kurz95: Kurz LC, Shah S, Frieden C, Nakra T, Stein RE, Drysdale GR, Evans CT, Srere PA (1995). "Catalytic strategy of citrate synthase: subunit interactions revealed as a consequence of a single amino acid change in the oxaloacetate binding site." Biochemistry 34(41);13278-88. PMID: 7577912

Lee97g: Lee S, Park C, Yim J (1997). "Characterization of citrate synthase purified from Drosophila melanogaster." Mol Cells 7(5);599-604. PMID: 9387145

Lenz71: Lenz H, Buckel W, Wunderwald P, Biedermann G, Buschmeier V, Eggerer H, Cornforth JW, Redmond JW, Mallaby R (1971). "Stereochemistry of si-citrate synthase and ATP-citrate-lyase reactions." Eur J Biochem 24(2);207-15. PMID: 5157292

LohleinWerhahn88: Lohlein-Werhahn G, Goepfert P, Eggerer H (1988). "Purification and properties of an archaebacterial enzyme: citrate synthase from Sulfolobus solfataricus." Biol Chem Hoppe Seyler 369(2);109-13. PMID: 3130075

Maurus03: Maurus R, Nguyen NT, Stokell DJ, Ayed A, Hultin PG, Duckworth HW, Brayer GD (2003). "Insights into the evolution of allosteric properties. The NADH binding site of hexameric type II citrate synthases." Biochemistry 42(19);5555-65. PMID: 12741811

Sievers97: Sievers M, Stockli M, Teuber M (1997). "Purification and properties of citrate synthase from Acetobacter europaeus." FEMS Microbiol Lett 146(1);53-8. PMID: 8997706

vanRooyen94: van Rooyen JP, Mienie LJ, Erasmus E, De Wet WJ, Ketting D, Duran M, Wadman SK (1994). "Identification of the stereoisomeric configurations of methylcitric acid produced by si-citrate synthase and methylcitrate synthase using capillary gas chromatography-mass spectrometry." J Inherit Metab Dis 17(6);738-47. PMID: 7707698

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Please cite the following article in publications resulting from the use of EcoCyc: Nucleic Acids Research 41:D605-12 2013
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