PATHWAY: hahs00020 Help
Entry
Name
Citrate cycle (TCA cycle) - Halanaeroarchaeum sp. HSR-CO
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
BRITE hierarchy
Pathway map
Ortholog table
Module
Other DBs
Organism
Halanaeroarchaeum sp. HSR-CO [GN:
hahs ]
Gene
HSRCO_2691 lpd3; Pyruvate/2-oxoglutarate dehydrogenase complex, dihydrolipoamide dehydrogenase (E3) component or related enzyme [KO:K00382 ] [EC:1.8.1.4 ]
HSRCO_1097 porA4; Pyruvate:ferredoxin oxidoreductase or related 2-oxoacid:ferredoxin oxidoreductase, alpha subunit and gamma [KO:K00174 ] [EC:1.2.7.3 1.2.7.11 ]
HSRCO_2134 sdhC; Succinate dehydrogenase/fumarate reductase, cytochrome b subunit [KO:K00241 ]
HSRCO_2133 sdhD; Succinate dehydrogenase, hydrophobic anchor subunit [KO:K00242 ]
HSRCO_2574 acoA3; Pyruvate/2-oxoglutarate/acetoin dehydrogenase complex, dehydrogenase (E1) component, eukaryotic type, alpha subunit [KO:K00161 ] [EC:1.2.4.1 ]
HSRCO_2688 acoA4; Pyruvate/2-oxoglutarate/acetoin dehydrogenase complex, dehydrogenase (E1) component, eukaryotic type, alpha subunit [KO:K00161 ] [EC:1.2.4.1 ]
HSRCO_2689 acoB3; Pyruvate/2-oxoglutarate/acetoin dehydrogenase complex, dehydrogenase (E1) component [KO:K00162 ] [EC:1.2.4.1 ]
HSRCO_0806 aceF2; Pyruvate/2-oxoglutarate dehydrogenase complex, dihydrolipoamide acyltransferase (E2) component [KO:K00627 ] [EC:2.3.1.12 ]
HSRCO_2690 aceF3; Pyruvate/2-oxoglutarate dehydrogenase complex, dihydrolipoamide acyltransferase (E2) component or related enzyme [KO:K00627 ] [EC:2.3.1.12 ]
HSRCO_0828 porA3; Pyruvate:ferredoxin oxidoreductase or related 2-oxoacid:ferredoxin oxidoreductase, alpha subunit [KO:K00169 ] [EC:1.2.7.1 ]
HSRCO_1975 porA5; Pyruvate:ferredoxin oxidoreductase or related 2-oxoacid:ferredoxin oxidoreductase, alpha subunit and gamma [KO:K00169 ] [EC:1.2.7.1 ]
HSRCO_0564 porB2; Pyruvate:ferredoxin oxidoreductase or related 2-oxoacid:ferredoxin oxidoreductase, beta subunit [KO:K00170 ] [EC:1.2.7.1 ]
HSRCO_0827 porB3; Pyruvate:ferredoxin oxidoreductase or related 2-oxoacid:ferredoxin oxidoreductase, beta subunit [KO:K00170 ] [EC:1.2.7.1 ]
HSRCO_1974 porB5; Pyruvate:ferredoxin oxidoreductase or related 2-oxoacid:ferredoxin oxidoreductase, beta subunit [KO:K00170 ] [EC:1.2.7.1 ]
HSRCO_0830 porG2; Pyruvate:ferredoxin oxidoreductase or related 2-oxoacid:ferredoxin oxidoreductase, gamma subunit [KO:K00172 ] [EC:1.2.7.1 ]
HSRCO_0561 porD; Pyruvate:ferredoxin oxidoreductase or related 2-oxoacid:ferredoxin oxidoreductase, delta subunit [KO:K00171 ] [EC:1.2.7.1 ]
HSRCO_0829 porD2; Pyruvate:ferredoxin oxidoreductase or related 2-oxoacid:ferredoxin oxidoreductase, delta subunit [KO:K00171 ] [EC:1.2.7.1 ]
Compound
C05125 2-(alpha-Hydroxyethyl)thiamine diphosphate
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
hahs00250 Alanine, aspartate and glutamate metabolism
hahs00280 Valine, leucine and isoleucine degradation
hahs00630 Glyoxylate and dicarboxylate metabolism
KO pathway
LinkDB
All DBs