MetaCyc Pathway: citrate degradation

Enzyme View:

Pathway diagram: citrate degradation

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

Some taxa known to possess this pathway include ? : Enterobacter aerogenes , Klebsiella pneumoniae , Rubrivivax gelatinosus

Expected Taxonomic Range: Bacteria

Citrate lyase is an anaerobic enzyme that catalyzes the cleavage of citrate to acetate and oxaloacetate [Nilekani83] (see citrate degradation). Because the citrate molecule is very stable, it has to be activated by forming a thioester bond with the enzyme before cleavage can take place.

The enzyme is a complex of three subunits (in a 6:6:6 configuration), one of them a dedicated acyl carrier protein (acp). The acp protein is synthesized in an apo form, and is converted to its fully active form in two steps - first, a holo form is generated by the covalent binding of the prosthetic group 2'-(5''-phosphoribosyl)-3'-dephospho-CoA to a serine residue. Next, the holo form is acetylated, either by EC, [citrate (pro-3S)-lyase] ligase, which uses acetate as the donor, or by EC, deacetyl-[citrate-(pro-3S)-lyase] S-acetyltransferase, that uses S-acetyl phosphopantetheine as the acetyl donor (see citrate lyase activation).

The α subunit of the citrate lyase is EC, citrate CoA-transferase, an enzyme that catalyzes the exchange of the bound acetyl group with a citrate molecule, generating a citryl-[holo citrate lyase acyl-carrier protein] and releasing an acetate molecule. The β subunit, EC, citryl-CoA lyase, catalyzes the subsequent step, cleaving the bound citryl group, releasing oxaloacetate and regenerating an acetyl-[holo citrate lyase acyl-carrier protein]. Since the active form is regenrated, the enzyme can continuously catalyze the cleavage reaction.

Genes complementary to the bacterial citrate lyase β subunit have been identified in the mouse and human genomes [Morikawa01]. The physiological role of these genes in eukaryotes is not known yet.

The sum of this pathway is described by EC, citrate (pro-3S)-lyase: citrate → acetate + oxaloacetate

Created 12-Sep-2008 by Caspi R , SRI International
Revised 01-Oct-2013 by Caspi R , SRI International


Morikawa01: Morikawa J, Nishimura Y, Uchida A, Tanaka T (2001). "Molecular cloning of novel mouse and human putative citrate lyase beta-subunit." Biochem Biophys Res Commun 289(5);1282-6. PMID: 11741334

Nilekani83: Nilekani S, SivaRaman C (1983). "Purification and properties of citrate lyase from Escherichia coli." Biochemistry 1983;22(20);4657-63. PMID: 6354265

Singh73: Singh M, Bottger B, Stewart C, Brooks GC, Srere PA (1973). "S-acetyl phosphopantetheine: deacetyl citrate lyase S-acetyl transferase from Klebsiella aerogenes." Biochem Biophys Res Commun 53(1);1-9. PMID: 4741546

Other References Related to Enzymes, Genes, Subpathways, and Substrates of this Pathway

Beyreuther78: Beyreuther K, Bohmer H, Dimroth P (1978). "Amino-acid sequence of citrate-lyase acyl-carrier protein from Klebsiella aerogenes." Eur J Biochem 87(1);101-10. PMID: 352686

Bott94: Bott M, Dimroth P (1994). "Klebsiella pneumoniae genes for citrate lyase and citrate lyase ligase: localization, sequencing, and expression." Mol Microbiol 14(2);347-56. PMID: 7830578

Hupperich90: Hupperich M, Henschen A, Eggerer H (1990). "Citrate lyase from Klebsiella pneumoniae. The complete primary structure of the acyl lyase subunit." Eur J Biochem 192(1);161-6. PMID: 2205500

Latendresse13: Latendresse M. (2013). "Computing Gibbs Free Energy of Compounds and Reactions in MetaCyc."

Singh76: Singh M, Srere PA (1976). "Subunit and chemical composition of citrate lyase from Klebsiella pneumoniae." J Biol Chem 251(10);2911-5. PMID: 773936

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Please cite the following article in publications resulting from the use of MetaCyc: Caspi et al, Nucleic Acids Research 42:D459-D471 2014
Page generated by SRI International Pathway Tools version 19.0 on Tue Oct 6, 2015, biocyc12.