Escherichia coli K-12 substr. MG1655 Protein Class: a [citrate-lyase] (citryl form)

Superclasses: a modified protein

Citrate lyase, an anaerobic enzyme, catalyzes the cleavage of citrate to acetate and oxaloacetate [Nilekani83]. The citrate molecule is very stable, and needs to be activated prior to cleavage by forming a thioester bond with the enzyme.

The enzyme is a complex of three subunits (in a 6:6:6 configuration), one of them a dedicated acyl carrier protein (acp). It is synthesized in an apo form, and is converted to its holo form by the covalent binding of the unusual prosthetic group 2'-(5''-phosphoribosyl)-3'-dephospho-CoA to the [acp] component, resulting in a [citrate-lyase]. However, this holo form is still not fully active - in order to be active, the prosthetic group needs to be acetylated, a reaction catalyzed by the citC-encoded citrate lyase synthetase, which generates an acetyl-[holo citrate lyase acyl-carrier protein].

The α subunit of the citrate lyase is a citrate-[acp] transferase that catalyzes the exchange of the bound acetyl group with a citrate molecule, generating a [citrate-lyase] (citryl form) and releasing an acetate molecule. The β subunit, which is a citryl-[acp] 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.

Alternative forms of a [citrate-lyase] (citryl form):
a [citrate-lyase] (extended summary available)
a citryl-[holo citrate lyase acyl-carrier protein] (extended summary available)

Gene-Reaction Schematic

Gene-Reaction Schematic


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

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Please cite the following article in publications resulting from the use of EcoCyc: Nucleic Acids Research 41:D605-12 2013
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