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Entry
sce00020                    Pathway                                

Name
Citrate cycle (TCA cycle) - Saccharomyces cerevisiae (budding yeast)
Description
The citrate cycle (TCA cycle, Krebs cycle) is an important aerobic pathway for the final steps of the oxidation of carbohydrates and fatty acids. The cycle starts with acetyl-CoA, the activated form of acetate, derived from glycolysis and pyruvate oxidation for carbohydrates and from beta oxidation of fatty acids. The two-carbon acetyl group in acetyl-CoA is transferred to the four-carbon compound of oxaloacetate to form the six-carbon compound of citrate. In a series of reactions two carbons in citrate are oxidized to CO2 and the reaction pathway supplies NADH for use in the oxidative phosphorylation and other metabolic processes. The pathway also supplies important precursor metabolites including 2-oxoglutarate. At the end of the cycle the remaining four-carbon part is transformed back to oxaloacetate. According to the genome sequence data, many organisms seem to lack genes for the full cycle [MD:M00009], but contain genes for specific segments [MD:M00010 M00011].
Class
Metabolism; Carbohydrate metabolism
BRITE hierarchy
Pathway map
Citrate cycle (TCA cycle)
sce00020

All organismsOrtholog table
Module
Gluconeogenesis, oxaloacetate => fructose-6P [PATH:sce00020]
Citrate cycle (TCA cycle, Krebs cycle) [PATH:sce00020]
Citrate cycle, first carbon oxidation, oxaloacetate => 2-oxoglutarate [PATH:sce00020]
Citrate cycle, second carbon oxidation, 2-oxoglutarate => oxaloacetate [PATH:sce00020]
Pyruvate oxidation, pyruvate => acetyl-CoA [PATH:sce00020]
Other DBs
BSID: 
GO: 
Organism
Saccharomyces cerevisiae (budding yeast) [GN:sce]
Gene
CIT2; citrate (Si)-synthase CIT2 [KO:K01647] [EC:2.3.3.1]
CIT1; citrate (Si)-synthase CIT1 [KO:K01647] [EC:2.3.3.1]
CIT3; citrate (Si)-synthase CIT3 [KO:K01647] [EC:2.3.3.1]
ACO1; aconitate hydratase ACO1 [KO:K01681] [EC:4.2.1.3]
IDP3; isocitrate dehydrogenase (NADP(+)) IDP3 [KO:K00031] [EC:1.1.1.42]
IDP1; isocitrate dehydrogenase (NADP(+)) IDP1 [KO:K00031] [EC:1.1.1.42]
IDP2; isocitrate dehydrogenase (NADP(+)) IDP2 [KO:K00031] [EC:1.1.1.42]
IDH2; isocitrate dehydrogenase (NAD(+)) IDH2 [KO:K00030] [EC:1.1.1.41]
IDH1; isocitrate dehydrogenase (NAD(+)) IDH1 [KO:K00030] [EC:1.1.1.41]
KGD1; alpha-ketoglutarate dehydrogenase KGD1 [KO:K00164] [EC:1.2.4.2]
KGD2; alpha-ketoglutarate dehydrogenase KGD2 [KO:K00658] [EC:2.3.1.61]
IRC15; Irc15p [KO:K00382] [EC:1.8.1.4]
LPD1; dihydrolipoyl dehydrogenase [KO:K00382] [EC:1.8.1.4]
LSC1; succinate--CoA ligase (GDP-forming) subunit alpha [KO:K01899] [EC:6.2.1.5 6.2.1.4]
LSC2; succinate--CoA ligase (GDP-forming) subunit beta [KO:K01900] [EC:6.2.1.5 6.2.1.4]
succinate dehydrogenase SDH1b; K00234 succinate dehydrogenase (ubiquinone) flavoprotein subunit [EC:1.3.5.1] [KO:K00234] [EC:1.3.5.1]
SDH1; succinate dehydrogenase flavoprotein subunit SDH1 [KO:K00234] [EC:1.3.5.1]
SDH2; succinate dehydrogenase iron-sulfur protein subunit SDH2 [KO:K00235] [EC:1.3.5.1]
SHH3; protein SHH3 [KO:K00236]
SDH3; succinate dehydrogenase cytochrome b subunit SDH3 [KO:K00236]
SHH4; protein SHH4 [KO:K00237]
SDH4; succinate dehydrogenase membrane anchor subunit SDH4 [KO:K00237]
FUM1; fumarase FUM1 [KO:K01679] [EC:4.2.1.2]
MDH1; malate dehydrogenase MDH1 [KO:K00026] [EC:1.1.1.37]
MDH2; malate dehydrogenase MDH2 [KO:K00026] [EC:1.1.1.37]
MDH3; malate dehydrogenase MDH3 [KO:K00026] [EC:1.1.1.37]
PYC1; pyruvate carboxylase 1 [KO:K01958] [EC:6.4.1.1]
PYC2; pyruvate carboxylase 2 [KO:K01958] [EC:6.4.1.1]
PCK1; phosphoenolpyruvate carboxykinase PCK1 [KO:K01610] [EC:4.1.1.49]
PDA1; pyruvate dehydrogenase (acetyl-transferring) subunit E1 alpha [KO:K00161] [EC:1.2.4.1]
PDB1; pyruvate dehydrogenase (acetyl-transferring) subunit E1 beta [KO:K00162] [EC:1.2.4.1]
LAT1; dihydrolipoyllysine-residue acetyltransferase [KO:K00627] [EC:2.3.1.12]
Compound
C00022  
Pyruvate
C00024  
Acetyl-CoA
C00026  
2-Oxoglutarate
C00036  
Oxaloacetate
C00042  
Succinate
C00068  
Thiamin diphosphate
C00074  
Phosphoenolpyruvate
C00091  
Succinyl-CoA
C00122  
Fumarate
C00149  
(S)-Malate
C00158  
Citrate
C00311  
Isocitrate
C00417  
cis-Aconitate
C05125  
2-(alpha-Hydroxyethyl)thiamine diphosphate
C05379  
Oxalosuccinate
C05381  
3-Carboxy-1-hydroxypropyl-ThPP
C15972  
Enzyme N6-(lipoyl)lysine
C15973  
Enzyme N6-(dihydrolipoyl)lysine
C16254  
[Dihydrolipoyllysine-residue succinyltransferase] S-succinyldihydrolipoyllysine
C16255  
[Dihydrolipoyllysine-residue acetyltransferase] S-acetyldihydrolipoyllysine
Reference
(map 2)
  Authors
Nishizuka Y (ed).
  Title
[Metabolic Maps] (In Japanese)
  Journal
Tokyo Kagaku Dojin (1980)
Reference
(map 3)
  Authors
Nishizuka Y, Seyama Y, Ikai A, Ishimura Y, Kawaguchi A (eds).
  Title
[Cellular Functions and Metabolic Maps] (In Japanese)
  Journal
Tokyo Kagaku Dojin (1997)
Reference
  Authors
Michal G.
  Title
Biochemical Pathways
  Journal
Wiley (1999)
KO pathway
 

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