|Superclasses:||Reactions Classified By Conversion Type → Simple Reactions → Chemical Reactions|
|Reactions Classified By Substrate → Small-Molecule Reactions|
EC Number: 18.104.22.168
The reaction direction shown, that is, A + B ↔ C + D versus C + D ↔ A + B, 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, and some reactions have been computationally balanced for hydrogen by adding free protons. Please see the PGDB Concepts Guide for more information.
Mass balance status: Balanced.
Enzyme Commission Primary Name: citrate synthase (unknown stereospecificity)
Enzyme Commission Synonyms: citrate condensing enzyme, CoA-acetylating citrate oxaloacetate-lyase, citrate synθse, 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 22.214.171.124 to 126.96.36.199 in 2002.
Enzyme Commission Summary:
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 188.8.131.52, citrate (Si)-synthase and EC 184.108.40.206, citrate (Re)-synthase.
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
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
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
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