KEGG   PATHWAY: elo00020
Entry
elo00020                    Pathway                                
Name
Citrate cycle (TCA cycle) - Escherichia coli O44:H18 042 (EAEC)
Description
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].
Class
Metabolism; Carbohydrate metabolism
Pathway map
elo00020  Citrate cycle (TCA cycle)
elo00020

Module
elo_M00003  Gluconeogenesis, oxaloacetate => fructose-6P [PATH:elo00020]
elo_M00009  Citrate cycle (TCA cycle, Krebs cycle) [PATH:elo00020]
elo_M00010  Citrate cycle, first carbon oxidation, oxaloacetate => 2-oxoglutarate [PATH:elo00020]
elo_M00011  Citrate cycle, second carbon oxidation, 2-oxoglutarate => oxaloacetate [PATH:elo00020]
elo_M00307  Pyruvate oxidation, pyruvate => acetyl-CoA [PATH:elo00020]
Other DBs
GO: 0006099
Organism
Escherichia coli O44:H18 042 (EAEC) [GN:elo]
Gene
EC042_0737  gltA; citrate synthase [KO:K01647] [EC:2.3.3.1]
EC042_0790  putative aconitase [KO:K01681] [EC:4.2.1.3]
EC042_1401  acnA; aconitate hydratase 1 (citrate hydro-lyase 1) [KO:K01681] [EC:4.2.1.3]
EC042_0117  acnB; aconitate hydratase 2 (citrate hydro-lyase 2) [KO:K01682] [EC:4.2.1.3 4.2.1.99]
EC042_1207  icd; isocitrate dehydrogenase [NADP] [KO:K00031] [EC:1.1.1.42]
EC042_0743  sucA; 2-oxoglutarate dehydrogenase E1 component [KO:K00164] [EC:1.2.4.2]
EC042_0744  sucB; dihydrolipoamide succinyltransferase component (E2) [KO:K00658] [EC:2.3.1.61]
EC042_0115  lpdA; dihydrolipoyl dehydrogenase (E3 component of pyruvate and 2-oxoglutarate dehydrogenase complexes) [KO:K00382] [EC:1.8.1.4]
EC042_0746  sucD; succinyl-CoA synthetase alpha chain [KO:K01902] [EC:6.2.1.5]
EC042_0745  sucC; succinyl-CoA synthetase beta chain [KO:K01903] [EC:6.2.1.5]
EC042_0741  sdhA; succinate dehydrogenase flavoprotein subunit [KO:K00239] [EC:1.3.5.1]
EC042_0742  sdhB; succinate dehydrogenase iron-sulfur protein [KO:K00240] [EC:1.3.5.1]
EC042_0739  sdhC; succinate dehydrogenase cytochrome b-556 subunit [KO:K00241]
EC042_0740  sdhD; succinate dehydrogenase hydrophobic membrane anchor protein [KO:K00242]
EC042_4630  frdA; fumarate reductase flavoprotein subunit [KO:K00244] [EC:1.3.5.1]
EC042_4629  frdB; fumarate reductase iron-sulfur subunit [KO:K00245] [EC:1.3.5.1]
EC042_4628  frdC; fumarate reductase subunit C [KO:K00246]
EC042_4627  frdD; fumarate reductase subunit D [KO:K00247]
EC042_4487  fumB; fumarate hydratase class I, anaerobic [KO:K01676] [EC:4.2.1.2]
EC042_1780  fumA; fumarate hydratase class I, aerobic [KO:K01676] [EC:4.2.1.2]
EC042_0749  fumA; fumarate hydratase class I, aerobic [KO:K01676] [EC:4.2.1.2]
EC042_1779  fumC; fumarate hydratase class II [KO:K01679] [EC:4.2.1.2]
EC042_3138  putative transcriptional regulator [KO:K01774] [EC:4.2.1.2]
EC042_3521  mdh; malate dehydrogenase [KO:K00024] [EC:1.1.1.37]
EC042_2451  mqo; malate:quinone oxidoreductase [KO:K00116] [EC:1.1.5.4]
EC042_3664  pckA; phosphoenolpyruvate carboxykinase [ATP] [KO:K01610] [EC:4.1.1.49]
EC042_0113  aceE; pyruvate dehydrogenase E1 component [KO:K00163] [EC:1.2.4.1]
EC042_0114  aceF; dihydrolipoamide acetyltransferase component (E2) of pyruvate dehydrogenase [KO:K00627] [EC:2.3.1.12]
EC042_1524  probable pyruvate-flavodoxin oxidoreductase [KO:K03737] [EC:1.2.7.1 1.2.7.-]
Compound
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
Reference
  Authors
Nishizuka Y (ed).
  Title
[Metabolic Maps] (In Japanese)
  Journal
Tokyo Kagaku Dojin (1980)
Reference
  Authors
Nishizuka Y, Seyama Y, Ikai A, Ishimura Y, Kawaguchi A (eds).
  Title
[Cellular Functions and Metabolic Maps] (In Japanese)
  Journal
Tokyo Kagaku Dojin (1997)
Reference
  Authors
Michal G.
  Title
Biochemical Pathways
  Journal
Wiley (1999)
Related
pathway
elo00010  Glycolysis / Gluconeogenesis
elo00053  Ascorbate and aldarate metabolism
elo00061  Fatty acid biosynthesis
elo00071  Fatty acid degradation
elo00190  Oxidative phosphorylation
elo00220  Arginine biosynthesis
elo00250  Alanine, aspartate and glutamate metabolism
elo00280  Valine, leucine and isoleucine degradation
elo00350  Tyrosine metabolism
elo00470  D-Amino acid metabolism
elo00630  Glyoxylate and dicarboxylate metabolism
KO pathway
ko00020   

DBGET integrated database retrieval system