KEGG   PATHWAY: cyh00020
cyh00020                    Pathway                                

Citrate cycle (TCA cycle) - Rippkaea orientalis PCC 8802
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
Pathway map
cyh00020  Citrate cycle (TCA cycle)

cyh_M00003  Gluconeogenesis, oxaloacetate => fructose-6P [PATH:cyh00020]
cyh_M00010  Citrate cycle, first carbon oxidation, oxaloacetate => 2-oxoglutarate [PATH:cyh00020]
cyh_M00307  Pyruvate oxidation, pyruvate => acetyl-CoA [PATH:cyh00020]
Other DBs
GO: 0006099
Rippkaea orientalis PCC 8802 [GN:cyh]
Cyan8802_1408  2-methylcitrate synthase/citrate synthase II [KO:K01647] [EC:]
Cyan8802_1908  aconitate hydratase 2 [KO:K01682] [EC:]
Cyan8802_4014  isocitrate dehydrogenase, NADP-dependent [KO:K00031] [EC:]
Cyan8802_3968  dihydrolipoamide dehydrogenase [KO:K00382] [EC:]
Cyan8802_1216  CoA-binding domain protein [KO:K01902] [EC:]
Cyan8802_0543  ATP-grasp domain protein [KO:K01903] [EC:]
Cyan8802_1882  succinate dehydrogenase or fumarate reductase, flavoprotein subunit [KO:K00239] [EC:]
Cyan8802_0404  succinate dehydrogenase and fumarate reductase iron-sulfur protein [KO:K00240] [EC:]
Cyan8802_3151  CoB--CoM heterodisulfide reductase [KO:K00241]
Cyan8802_2918  fumarate hydratase, class II [KO:K01679] [EC:]
Cyan8802_0539  malate dehydrogenase, NAD-dependent [KO:K00024] [EC:]
Cyan8802_4079  phosphoenolpyruvate carboxykinase (ATP) [KO:K01610] [EC:]
Cyan8802_4191  pyruvate dehydrogenase (acetyl-transferring) E1 component, alpha subunit [KO:K00161] [EC:]
Cyan8802_3213  Transketolase central region [KO:K00162] [EC:]
Cyan8802_1261  catalytic domain of components of various dehydrogenase complexes [KO:K00627] [EC:]
Cyan8802_3966  pyruvate ferredoxin/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)
cyh00010  Glycolysis / Gluconeogenesis
cyh00053  Ascorbate and aldarate metabolism
cyh00061  Fatty acid biosynthesis
cyh00071  Fatty acid degradation
cyh00220  Arginine biosynthesis
cyh00250  Alanine, aspartate and glutamate metabolism
cyh00280  Valine, leucine and isoleucine degradation
cyh00350  Tyrosine metabolism
cyh00471  D-Glutamine and D-glutamate metabolism
cyh00630  Glyoxylate and dicarboxylate metabolism
KO pathway

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