In enzymology, a holo-ACP synthase (EC 2.7.7.61) is an enzyme that catalyzes the chemical reaction

2'-(5"-triphosphoribosyl)-3'-dephospho-CoA + apo-citrate lyase ${\displaystyle \rightleftharpoons }$ holo-citrate lyase + diphosphate

Thus, the two substrates of this enzyme are 2'-(5"-triphosphoribosyl)-3'-dephospho-CoA and apo-citrate lyase, whereas its two products are holo-citrate lyase and diphosphate.

This enzyme belongs to the family of transferases, specifically those transferring phosphorus-containing nucleotide groups (nucleotidyltransferases). The systematic name of this enzyme class is 2'-(5"-triphosphoribosyl)-3'-dephospho-CoA:apo-citrate lyase adenylyltransferase. Other names in common use include 2'-(5"-phosphoribosyl)-3'-dephospho-CoA transferase, 2'-(5"-triphosphoribosyl)-3'-dephospho-CoA:apo-citrate lyase, and CitX. This enzyme participates in two-component system - general.

As of late 2007, only one structure has been solved for this class of enzymes, with the PDB accession code 2BDD.

• Schneider K, Dimroth P, Bott M (2000). "Biosynthesis of the prosthetic group of citrate lyase" (PDF). Biochemistry. 39 (31): 9438–50. doi:10.1021/bi000401r. PMID 10924139.
• Schneider K, Dimroth P, Bott M (2000). "Identification of triphosphoribosyl-dephospho-CoA as precursor of the citrate lyase prosthetic group". FEBS Lett. 483 (2–3): 165–8. doi:10.1016/S0014-5793(00)02105-0. PMID 11042274. S2CID 38809036.