Catalyzes two sequential steps in the biosynthesis of coenzyme A. In the first step cysteine is conjugated to 4'-phosphopantothenate to form 4-phosphopantothenoylcysteine (PubMed:11278255, PubMed:12140293, PubMed:14686929). In the second step the latter compound is decarboxylated to form 4'-phosphopantotheine (PubMed:10922366, PubMed:11358972). H(+) + N-[(R)-4-phosphopantothenoyl]-L-cysteine = (R)-4'-phosphopantetheine + CO2 (R)-4'-phosphopantothenate + CTP + L-cysteine = CMP + diphosphate + H(+) + N-[(R)-4-phosphopantothenoyl]-L-cysteine Binds 1 FMN per subunit. Cofactor biosynthesis; coenzyme A biosynthesis; CoA from (R)-pantothenate: step 2/5. Cofactor biosynthesis; coenzyme A biosynthesis; CoA from (R)-pantothenate: step 3/5. Homododecamer (PubMed:10922366, PubMed:11358972). The CoaC domain is responsible for dodecamer formation (PubMed:11358972). The CoaB domain forms homodimers (PubMed:12140293). In the N-terminal section; belongs to the HFCD (homo-oligomeric flavin containing Cys decarboxylase) superfamily. In the C-terminal section; belongs to the PPC synthetase family. Extended N-terminus.