Reversibly transfers an adenylyl group from ATP to 4'-phosphopantetheine, yielding dephospho-CoA (dPCoA) and pyrophosphate (PubMed:10480925, PubMed:17873050). CoA is not a substrate for the enzyme (PubMed:10480925). (R)-4'-phosphopantetheine + ATP + H(+) = 3'-dephospho-CoA + diphosphate Crystallized in the absence of Mg(2+), the catalytic metal is not bound by the protein but probably by non-esterified oxygen atoms from ATP and/or ordered H(2)O (PubMed:11812124). Feedback inhibited by CoA, which is competitive with ATP, 4'-phosphopantetheine and 3'-dephospho-CoA (PubMed:17873050, PubMed:10480925). Binds 0.5 CoA tightly per monomer in the same position as 3'-dephospho-CoA but in a different fashion (PubMed:12837781, PubMed:17873050). Is inhibited by the very potent and specific inhibitor PTX042695 dipeptide, with an IC(50) of 6 nM, a compound which has no activity against porcine PPAT (PubMed:12750020). A series of pyrazoloquinolones were also characterized as ATP-competitive inhibitors of PPAT (PubMed:20486930). kcat is 1.37 sec(-1) for the forward reaction, with ATP and pantetheine 4'-phosphate as substrates (PubMed:17873050). kcat is 3.3 sec(-1) for the reverse reaction, with diphosphate and 3'-dephospho-CoA as substrates (PubMed:10480925). kcat is 1.37 sec(-1) for the reverse reaction, with diphosphate and 3'-dephospho-CoA as substrates (PubMed:17873050). Optimum pH is 6.9. Cofactor biosynthesis; coenzyme A biosynthesis; CoA from (R)-pantothenate: step 4/5. Homohexamer, a dimerized trimer with a solvent channel through the middle (PubMed:10480925, PubMed:10205156, PubMed:11812124, PubMed:12837781, PubMed:17873050). In crystals only 1 trimer is seen to bind substrate/product at a time (PubMed:10205156, PubMed:11812124). The crystal structures in complex with substrates suggest the enzyme stabilizes the transition state but the functional groups of the enzyme are not directly involved in reaction catalysis. Belongs to the bacterial CoaD family. Was originally thought to have an essential function in lipopolysaccharide biosynthesis.