KEGG   PATHWAY: mmd00020Help
mmd00020                    Pathway                                

Citrate cycle (TCA cycle) - Methanococcus maripaludis X1
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
mmd00020  Citrate cycle (TCA cycle)

Ortholog table
mmd_M00307  Pyruvate oxidation, pyruvate => acetyl-CoA [PATH:mmd00020]
Other DBs
BSID: 538707
GO: 0006099
Methanococcus maripaludis X1 [GN:mmd]
GYY_07485  FAD-dependent pyridine nucleotide-disulfide oxidoreductase [KO:K00382] [EC:]
GYY_00015  2-oxoglutarate ferredoxin oxidoreductase subunit alpha [KO:K00174] [EC:]
GYY_01570  oxidoreductase family protein member subunit alpha [KO:K00174] [EC:]
GYY_01565  2-oxoacid ferredoxin oxidoreductase subunit beta [KO:K00175] [EC:]
GYY_07405  2-oxoglutarate ferredoxin oxidoreductase subunit beta [KO:K00175] [EC:]
GYY_07400  2-oxoglutarate ferredoxin oxidoreductase subunit gamma [KO:K00177] [EC:]
GYY_09295  4Fe-4S ferredoxin iron-sulfur binding domain-containing protein [KO:K00176] [EC:]
GYY_05600  succinyl-CoA synthetase subunit alpha [KO:K01902] [EC:]
GYY_06350  succinyl-CoA synthetase, beta subunit [KO:K01903] [EC:]
GYY_00660  fumarate hydratase [KO:K01677] [EC:]
GYY_08585  Fe-S type hydro-lyase tartrate/fumarate subunit beta [KO:K01678] [EC:]
GYY_03235  malate dehydrogenase [KO:K00024] [EC:]
GYY_01750  pyruvate carboxylase subunit A [KO:K01959] [EC:]
GYY_01745  pyruvate carboxylase subunit B [KO:K01960] [EC:]
GYY_08365  pyruvate flavodoxin/ferredoxin oxidoreductase domain protein [KO:K00169] [EC:]
GYY_08360  pyruvate ferredoxin oxidoreductase subunit beta [KO:K00170] [EC:]
GYY_08375  pyruvate ferredoxin oxidoreductase subunit gamma [KO:K00172] [EC:]
GYY_08370  pyruvate ferredoxin/flavodoxin oxidoreductase, delta subunit [KO:K00171] [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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