-!- Essential, along with EC 2.3.1.38, for the initiation of fatty-acid biosynthesis in bacteria. -!- Also provides the malonyl groups for polyketide biosynthesis. -!- The product of the reaction, malonyl-ACP, is an elongation substrate in fatty-acid biosynthesis. -!- In Mycobacterium tuberculosis, holo-ACP (the product of EC 2.7.8.7) is the preferred substrate. -!- This enzyme also forms part of the multienzyme complexes EC 4.1.1.88 and EC 4.1.1.89. -!- Malonylation of ACP is immediately followed by decarboxylation within the malonate-decarboxylase complex to yield acetyl-ACP, the catalytically active species of the decarboxylase. -!- In the enzyme from Klebsiella pneumoniae, methylmalonyl-CoA can also act as a substrate but acetyl-CoA cannot whereas the enzyme from Pseudomonas putida can use both as substrates. -!- The ACP subunit found in fatty-acid biosynthesis contains a pantetheine-4'-phosphate prosthetic group; that from malonate decarboxylase also contains pantetheine-4'-phosphate but in the form of a 2'-(5-triphosphoribosyl)-3'-dephospho-CoA prosthetic group.