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etc00020                    Pathway                                

Citrate cycle (TCA cycle) - Edwardsiella piscicida C07-087
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].
Metabolism; Carbohydrate metabolism
BRITE hierarchy
Pathway map
etc00020  Citrate cycle (TCA cycle)

Ortholog table
etc_M00003  Gluconeogenesis, oxaloacetate => fructose-6P [PATH:etc00020]
etc_M00009  Citrate cycle (TCA cycle, Krebs cycle) [PATH:etc00020]
etc_M00010  Citrate cycle, first carbon oxidation, oxaloacetate => 2-oxoglutarate [PATH:etc00020]
etc_M00011  Citrate cycle, second carbon oxidation, 2-oxoglutarate => oxaloacetate [PATH:etc00020]
etc_M00307  Pyruvate oxidation, pyruvate => acetyl-CoA [PATH:etc00020]
Other DBs
GO: 0006099
Edwardsiella piscicida C07-087 [GN:etc]
ETAC_12445  gltA; type II citrate synthase [KO:K01647] [EC:]
ETAC_03215  bifunctional aconitate hydratase 2/2-methylisocitrate dehydratase [KO:K01682] [EC:]
ETAC_09490  isocitrate dehydrogenase [KO:K00031] [EC:]
ETAC_09740  Isocitrate dehydrogenase [KO:K00031] [EC:]
ETAC_12420  sucA; 2-oxoglutarate dehydrogenase E1 component [KO:K00164] [EC:]
ETAC_12415  Dihydrolipoamide succinyltransferase component (E2) of 2-oxoglutarate dehydrogenase complex [KO:K00658] [EC:]
ETAC_03205  dihydrolipoamide dehydrogenase [KO:K00382] [EC:]
ETAC_16715  dihydrolipoamide dehydrogenase [KO:K00382] [EC:]
ETAC_12405  succinyl-CoA ligase subunit alpha [KO:K01902] [EC:]
ETAC_12410  sucC; succinyl-CoA synthetase subunit beta [KO:K01903] [EC:]
ETAC_12430  sdhA; succinate dehydrogenase flavoprotein subunit [KO:K00239] [EC:]
ETAC_12425  Succinate dehydrogenase iron-sulfur protein [KO:K00240] [EC:]
ETAC_12440  sdhC; succinate dehydrogenase cytochrome b556 large membrane subunit [KO:K00241]
ETAC_12435  Succinate dehydrogenase hydrophobic membrane anchor protein [KO:K00242]
ETAC_01470  fumarate reductase flavoprotein subunit [KO:K00244] [EC:]
ETAC_01465  fumarate reductase iron-sulfur subunit [KO:K00245] [EC:]
ETAC_01460  fumarate reductase subunit C [KO:K00246]
ETAC_01455  fumarate reductase subunit D [KO:K00247]
ETAC_10045  Fumarate hydratase class I [KO:K01676] [EC:]
ETAC_07845  fumarate hydratase [KO:K01679] [EC:]
ETAC_01705  malate dehydrogenase [KO:K00024] [EC:]
ETAC_15635  phosphoenolpyruvate carboxykinase [KO:K01610] [EC:]
ETAC_03195  aceE; pyruvate dehydrogenase subunit E1 [KO:K00163] [EC:]
ETAC_03200  aceF; pyruvate dehydrogenase dihydrolipoyltransacetylase [KO:K00627] [EC:]
ETAC_12055  Pyruvate-flavodoxin oxidoreductase [KO:K03737] [EC:1.2.7.-]
ETAC_08170  Pyruvate-flavodoxin oxidoreductase [KO:K03737] [EC:1.2.7.-]
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
(map 2)
Nishizuka Y (ed).
[Metabolic Maps] (In Japanese)
Tokyo Kagaku Dojin (1980)
(map 3)
Nishizuka Y, Seyama Y, Ikai A, Ishimura Y, Kawaguchi A (eds).
[Cellular Functions and Metabolic Maps] (In Japanese)
Tokyo Kagaku Dojin (1997)
Michal G.
Biochemical Pathways
Wiley (1999)
KO pathway

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