KEGG   PATHWAY: naz00020Help
naz00020                    Pathway                                

Citrate cycle (TCA cycle) - 'Nostoc azollae' 0708
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
naz00020  Citrate cycle (TCA cycle)

Ortholog table
naz_M00010  Citrate cycle, first carbon oxidation, oxaloacetate => 2-oxoglutarate [PATH:naz00020]
naz_M00307  Pyruvate oxidation, pyruvate => acetyl-CoA [PATH:naz00020]
Other DBs
GO: 0006099
'Nostoc azollae' 0708 [GN:naz]
Aazo_0404  2-methylcitrate synthase/citrate synthase II [KO:K01647] [EC:]
Aazo_3996  aconitate hydratase 2 [KO:K01682] [EC:]
Aazo_1215  isocitrate dehydrogenase, NADP-dependent [KO:K00031] [EC:]
Aazo_0099  dihydrolipoamide dehydrogenase [KO:K00382] [EC:]
Aazo_1151  CoA-binding domain protein [KO:K01902] [EC:]
Aazo_1152  ATP-grasp domain protein [KO:K01903] [EC:]
Aazo_1206  succinate dehydrogenase or fumarate reductase, flavoprotein subunit [KO:K00239] [EC:]
Aazo_0058  succinate dehydrogenase and fumarate reductase iron-sulfur protein [KO:K00240] [EC:]
Aazo_1632  CoB--CoM heterodisulfide reductase [KO:K00241]
Aazo_2058  pyruvate dehydrogenase (acetyl-transferring) E1 component, alpha subunit [KO:K00161] [EC:]
Aazo_4540  Transketolase central region [KO:K00162] [EC:]
Aazo_1439  catalytic domain of components of various dehydrogenase complexes [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)
naz00010  Glycolysis / Gluconeogenesis
naz00053  Ascorbate and aldarate metabolism
naz00061  Fatty acid biosynthesis
naz00071  Fatty acid degradation
naz00220  Arginine biosynthesis
naz00250  Alanine, aspartate and glutamate metabolism
naz00280  Valine, leucine and isoleucine degradation
naz00350  Tyrosine metabolism
naz00471  D-Glutamine and D-glutamate metabolism
naz00630  Glyoxylate and dicarboxylate metabolism
KO pathway
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