KEGG   PATHWAY: rrh00020Help
rrh00020                    Pathway                                

Citrate cycle (TCA cycle) - Rickettsia rickettsii Hauke
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
rrh00020  Citrate cycle (TCA cycle)

Ortholog table
rrh_M00009  Citrate cycle (TCA cycle, Krebs cycle) [PATH:rrh00020]
rrh_M00010  Citrate cycle, first carbon oxidation, oxaloacetate => 2-oxoglutarate [PATH:rrh00020]
rrh_M00011  Citrate cycle, second carbon oxidation, 2-oxoglutarate => oxaloacetate [PATH:rrh00020]
rrh_M00307  Pyruvate oxidation, pyruvate => acetyl-CoA [PATH:rrh00020]
Other DBs
BSID: 566358
GO: 0006099
Rickettsia rickettsii Hauke [GN:rrh]
RPM_07195  gltA; type II citrate synthase [KO:K01647] [EC:]
RPM_06765  aconitate hydratase [KO:K01681] [EC:]
RPM_01985  isocitrate dehydrogenase [KO:K00031] [EC:]
RPM_01295  sucA; 2-oxoglutarate dehydrogenase E1 component [KO:K00164] [EC:]
RPM_01285  dihydrolipoamide succinyltransferase [KO:K00658] [EC:]
RPM_04295  dihydrolipoamide dehydrogenase [KO:K00382] [EC:]
RPM_06795  dihydrolipoamide dehydrogenase [KO:K00382] [EC:]
RPM_03335  succinyl-CoA synthetase subunit alpha [KO:K01902] [EC:]
RPM_03340  sucC; succinyl-CoA synthetase subunit beta [KO:K01903] [EC:]
RPM_00970  sdhA; succinate dehydrogenase flavoprotein subunit [KO:K00239] [EC:]
RPM_00430  sdhB; succinate dehydrogenase iron-sulfur subunit [KO:K00240] [EC:]
RPM_00960  succinate dehydrogenase cytochrome b-556 subunit [KO:K00241]
RPM_00965  succinate dehydrogenase hydrophobic membrane anchor protein [KO:K00242]
RPM_05620  fumC; fumarate hydratase [KO:K01679] [EC:]
RPM_02915  malate dehydrogenase [KO:K00024] [EC:]
RPM_01950  pyruvate dehydrogenase e1 component, alpha subunit precursor [KO:K00161] [EC:]
RPM_01955  pyruvate dehydrogenase subunit beta [KO:K00162] [EC:]
RPM_03895  branched-chain alpha-keto acid dehydrogenase subunit E2 [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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