This view shows enzymes only for those organisms listed below, in the list of taxa known to possess the pathway. If an enzyme name is shown in bold, there is experimental evidence for this enzymatic activity.
|Superclasses:||Degradation/Utilization/Assimilation → Carboxylates Degradation → Acetate Formation|
|Generation of Precursor Metabolites and Energy → Fermentation → Acetate Formation|
Some taxa known to possess this pathway include : Entamoeba histolytica , Giardia intestinalis , Haloarcula marismortui , Halococcus saccharolyticus , Haloferax volcanii , Halorubrum saccharovorum , Pyrococcus furiosus , Selenomonas ruminantium
Many eubacteria produce acetate from acetyl CoA via a two-step pathway in which acetyl phosphate occurs as an intermediate (see acetate formation from acetyl-CoA I) [Brown77]. The second reaction, catalyzed by acetate kinase, results in the generation of ATP from ADP.
In archea [Mai96], some eubacteria (such as Selenomonas ruminantium [Michel90]), and amitochondriate protists (such as Entamoeba histolytica [Reeves77] and Giardia intestinalis [Sanchez96]) acetate is produced from acetyl CoA in a single step via the enzyme acetyl-CoA synthetase (ADP-forming). In this process, the formation of acetate from acetyl CoA concomitantly produces ATP from ADP (see acetate formation from acetyl-CoA II).
A third pathway (acetate formation from acetyl-CoA III (succinate)) is found in a diverse group of organisms, which includes the hydrogenosome-containing trichomonads (such as Tritrichomonas suis and Trichomonas vaginalis [Steinbuchel86]), some anaerobic fungi (such as Neocallimastix sp. LM-2[MarvinSikkema93]), the parasitic helminth Fasciola hepatica [Barrett78, vanVugt79, Saz96] and the trypanosomatides [Van98, Riviere04]. Theser organisms produce acetate from acetyl CoA by acetyl:succinate CoA-transferase (ASCT), an enzyme that transfers the CoA group from acetyl-CoA to succinate, producing succinyl-CoA. succinyl-CoA is restored to succinate by succinyl-CoA synthetase, a TCA cycle enzyme that generates ATP from ADP.
About This Pathway
The thermophilic archaeon Pyrococcus furiosus is a strict anaerobe, capable of utilizing pyruvate, sugars and complex organic compounds as carbon and energy sources. When sulfur is available, the organism uses it as an electron acceptor for anaerobic respiration. When sulfur is not available, it can grow by fermentation of peptides, carbohydrates, and pyruvate.
Pyrococcus furiosus employs a modified glycolytic pathway for the catabolism of sugars, as shown in the pathway glycolysis V (Pyrococcus) [Mai96, Glasemacher97]. acetyl-CoA is converted to acetate in a single step, catalyzed by the enzyme acetyl-CoA synthetase (ADP-forming). In most other organisms, this conversion is catalyzed in two steps, via acetyl phosphate.
The same pathway has also been described in halophilic archaea, including Haloarcula marismortui [Brasen04], Halococcus saccharolyticus, Haloferax volcanii and Halorubrum saccharovorum [Brasen01]. When these organisms grow on glucose they form acetate in a reaction catalyzed by acetyl-CoA synthetase (ADP-forming). The acetate is excreted into the medium. In stationary phase the cells consume the excreted acetate, in a pathway that involves its conversion back to acetyl-CoA. This reverse reaction is not catalyzed by acetyl-CoA synthetase (ADP-forming), but by acetyl-CoA synthetase (AMP-forming) (see acetate conversion to acetyl-CoA) [Brasen01].
Similar pathways from pyruvate to acetate have also been described in the eukaryotic human parasite Entamoeba histolytica [Reeves77], and in the eubacterium Selenomonas ruminantium [Melville88, Michel90].
Superpathways: pyruvate fermentation to acetate III , benzoate fermentation (to acetate and cyclohexane carboxylate) , crotonate fermentation (to acetate and cyclohexane carboxylate) , pyruvate fermentation to acetate and alanine
Brasen04: Brasen C, Schonheit P (2004). "Regulation of acetate and acetyl-CoA converting enzymes during growth on acetate and/or glucose in the halophilic archaeon Haloarcula marismortui." FEMS Microbiol Lett 241(1);21-6. PMID: 15556705
Glasemacher97: Glasemacher J, Bock AK, Schmid R, Schonheit P (1997). "Purification and properties of acetyl-CoA synthetase (ADP-forming), an archaeal enzyme of acetate formation and ATP synthesis, from the hyperthermophile Pyrococcus furiosus." Eur J Biochem 1997;244(2);561-7. PMID: 9119024
Mai96: Mai X, Adams MW (1996). "Purification and characterization of two reversible and ADP-dependent acetyl coenzyme A synthetases from the hyperthermophilic archaeon Pyrococcus furiosus." J Bacteriol 1996;178(20);5897-903. PMID: 8830684
MarvinSikkema93: Marvin-Sikkema FD, Pedro Gomes TM, Grivet JP, Gottschal JC, Prins RA (1993). "Characterization of hydrogenosomes and their role in glucose metabolism of Neocallimastix sp. L2." Arch Microbiol 160(5);388-96. PMID: 8257282
Michel90: Michel, T. A., Macy, J. M. (1990). "Purification of an enzyme responsible for acetate formation from acetyl coenzyme A in Selenomonas ruminatium." FEMS Microbiology Letters 68 (1-2): 189-194.
Reeves77: Reeves RE, Warren LG, Susskind B, Lo HS (1977). "An energy-conserving pyruvate-to-acetate pathway in Entamoeba histolytica. Pyruvate synthase and a new acetate thiokinase." J Biol Chem 252(2);726-31. PMID: 13076
Riviere04: Riviere L, van Weelden SW, Glass P, Vegh P, Coustou V, Biran M, van Hellemond JJ, Bringaud F, Tielens AG, Boshart M (2004). "Acetyl:succinate CoA-transferase in procyclic Trypanosoma brucei. Gene identification and role in carbohydrate metabolism." J Biol Chem 279(44);45337-46. PMID: 15326192
Sanchez96: Sanchez LB, Muller M (1996). "Purification and characterization of the acetate forming enzyme, acetyl-CoA synthetase (ADP-forming) from the amitochondriate protist, Giardia lamblia." FEBS Lett 378(3);240-4. PMID: 8557109
Van98: Van Hellemond JJ, Opperdoes FR, Tielens AG (1998). "Trypanosomatidae produce acetate via a mitochondrial acetate:succinate CoA transferase." Proc Natl Acad Sci U S A 95(6);3036-41. PMID: 9501211
vanVugt79: van Vugt F, van der Meer P, van den Bergh SG (1979). "The formation of propionate and acetate as terminal processes in the energy metabolism of the adult liver fluke Fasciola hepatica." Int J Biochem 10(1);11-8. PMID: 421954
Musfeldt99: Musfeldt M, Selig M, Schonheit P (1999). "Acetyl coenzyme A synthetase (ADP forming) from the hyperthermophilic Archaeon pyrococcus furiosus: identification, cloning, separate expression of the encoding genes, acdAI and acdBI, in Escherichia coli, and in vitro reconstitution of the active heterotetrameric enzyme from its recombinant subunits." J Bacteriol 181(18);5885-8. PMID: 10482538
Rubio06: Rubio S, Larson TR, Gonzalez-Guzman M, Alejandro S, Graham IA, Serrano R, Rodriguez PL (2006). "An Arabidopsis mutant impaired in coenzyme A biosynthesis is sugar dependent for seedling establishment." Plant Physiol 140(3);830-43. PMID: 16415216
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