Figure 16.

CoA biosynthesis. The five-step pathway starts with phosphorylation of pantothenic acid to 4′-phosphopantothenate by pantothenate-kinase (PANK). Then, 4′-phosphopantothenate condensates with cysteine. This reaction is catalyzed by phosphopantothenoylcysteine synthetase and gives rise to N-[(R)-4’-phosphopantothenoyl]-L-cysteine. This product is subsequently decarboxylated in presence of phosphopantothenoylcysteine decarboxylase to generate phosphopantetheine. Last two steps consist of phosphorylation of 4′-phosphopantetheine to form dephosphopantetheine and phosphorylation of 3′-hydroxy group of ribose to form CoA. Both reactions are catalyzed by an enzyme called COASY, which exhibit two enzymatic activities: 4′-phosphopantetheine adenyltransferase (catalyzes the fourth reaction) and dephospho-CoA kinase (catalyzes the fifth reaction).