KEGG   PATHWAY: shw00020Help
shw00020                    Pathway                                

Citrate cycle (TCA cycle) - Shewanella sp. W3-18-1
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
shw00020  Citrate cycle (TCA cycle)

Ortholog table
shw_M00003  Gluconeogenesis, oxaloacetate => fructose-6P [PATH:shw00020]
shw_M00009  Citrate cycle (TCA cycle, Krebs cycle) [PATH:shw00020]
shw_M00010  Citrate cycle, first carbon oxidation, oxaloacetate => 2-oxoglutarate [PATH:shw00020]
shw_M00011  Citrate cycle, second carbon oxidation, 2-oxoglutarate => oxaloacetate [PATH:shw00020]
shw_M00307  Pyruvate oxidation, pyruvate => acetyl-CoA [PATH:shw00020]
Other DBs
BSID: 44633
GO: 0006099
Shewanella sp. W3-18-1 [GN:shw]
Sputw3181_1734  citrate synthase [KO:K01647] [EC:]
Sputw3181_0534  aconitase [KO:K01682] [EC:]
Sputw3181_1779  isocitrate dehydrogenase, NADP-dependent [KO:K00031] [EC:]
Sputw3181_2820  Isocitrate dehydrogenase (NAD(+)) [KO:K00030] [EC:]
Sputw3181_1739  2-oxoglutarate dehydrogenase E1 component [KO:K00164] [EC:]
Sputw3181_1740  2-oxoglutarate dehydrogenase E2 component [KO:K00658] [EC:]
Sputw3181_0528  dihydrolipoamide dehydrogenase [KO:K00382] [EC:]
Sputw3181_1742  succinyl-CoA synthetase (ADP-forming) alpha subunit [KO:K01902] [EC:]
Sputw3181_1741  succinyl-CoA synthetase (ADP-forming) beta subunit [KO:K01903] [EC:]
Sputw3181_1737  succinate dehydrogenase subunit A [KO:K00239] [EC:]
Sputw3181_1738  succinate dehydrogenase subunit B [KO:K00240] [EC:]
Sputw3181_1735  succinate dehydrogenase subunit C [KO:K00241]
Sputw3181_1736  succinate dehydrogenase subunit D [KO:K00242]
Sputw3181_3267  flavocytochrome c [KO:K00244] [EC:]
Sputw3181_0204  succinate dehydrogenase subunit A [KO:K00244] [EC:]
Sputw3181_0500  succinate dehydrogenase subunit A [KO:K00244] [EC:]
Sputw3181_0203  succinate dehydrogenase subunit B [KO:K00245] [EC:]
Sputw3181_0501  succinate dehydrogenase subunit B [KO:K00245] [EC:]
Sputw3181_0202  fumarate reductase, subunit C [KO:K00246]
Sputw3181_0498  fumarate reductase respiratory complex, transmembrane subunit [KO:K00246]
Sputw3181_0499  fumarate reductase respiratory complex, transmembrane subunit [KO:K00246]
Sputw3181_0201  succinate dehydrogenase subunit D [KO:K00247]
Sputw3181_0198  fumarase [KO:K01676] [EC:]
Sputw3181_2218  fumarase [KO:K01676] [EC:]
Sputw3181_3574  fumarate hydratase, class II [KO:K01679] [EC:]
Sputw3181_0722  malate dehydrogenase (NAD) [KO:K00024] [EC:]
Sputw3181_3708  Phosphoenolpyruvate carboxykinase (ATP) [KO:K01610] [EC:]
Sputw3181_0526  2-oxo-acid dehydrogenase E1 subunit, homodimeric type [KO:K00163] [EC:]
Sputw3181_0527  pyruvate dehydrogenase complex dihydrolipoamide acetyltransferase [KO:K00627] [EC:]
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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