ATP citrate lyase is an enzyme that represents an important step in fatty acid biosynthesis.^[1] This step in fatty acid biosynthesis occurs because ATP citrate lyase is the link between the metabolism of carbohydrates (which causes energy) and the production of fatty acids.^[2]

Function

ATP citrate lyase is the primary enzyme responsible for the synthesis of cytosolic acetyl-CoA in many tissues. The enzyme is a tetramer of apparently identical subunits. The product, acetyl-CoA, serves several important biosynthetic pathways, including lipogenesis and cholesterogenesis.^[3] It is activated by insulin.^[4] ATP-citrate lyase is also responsible for catalyzing the conversion of citrate and CoA into acetyl-CoA and oxaloacetate, along with the hydrolysis of ATP.^[2]

Reaction

In the presence of ATP and Coenzyme A, citrate lyase catalyzes the cleavage of citrate to yield acetyl CoA, oxaloacetate, ADP, and orthophosphate:

citrate + ATP + CoA + H2O-->oxaloacetate + Acetyl-CoA + ADP + Pi.

This enzyme was formerly listed as EC 4.1.3.8.^[5]

Location

The enzyme is cytosolic in plants^[6] and animals.

Structure

The enzyme is composed of two subunits in green plants (including Chlorophyceae, Marchantimorpha, Bryopsida, Pinaceae, monocotyledons, and eudicots), species of fungi, Glaucophytes, Chlamydomonas, and prokaryotes.

Animal ACL enzymes are homomeric, presumably an evolutionary fusion of the ACLA and ACLB genes probably occurred early in the evolutionary history of this kingdom.^[6]

A structure of human ATP citrate lyase was determined using X-ray diffraction to a resolution of 2.10 . The enzyme is composed of two polymer chains which are polypeptides. Chain A of the first polymer is 425 amino acids in length. Chain B of the second polymer is 334 amino acids in length.^[2]

References

Further reading

External links

Ramachandran Plot of ATP Citrate Lyase http://www.rcsb.org/pdb/images/3MWD_ram_m_500.pdf

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