Role of prokaryotic type I and III pantothenate kinases in the coenzyme A biosynthetic pathway of Bacillus subtilis.

Pantothenate kinases (CoaAs) catalyze the phosphorylation of pantothenate in the first step of the coenzyme A (CoA) biosynthetic pathway. These bacterial enzymes have been categorized into 3 types, the prokaryotic type I, II, and III CoaAs. Bacteria typically carry a single CoaA gene on their genome, but Bacillus subtilis possesses 2 proteins homologous to type I and III CoaAs, known as BsCoaA and BsCoaX, respectively. Both recombinant proteins exhibited the expected kinase activity and the characteristic properties of type I and III CoaAs, i.e., regulation by CoASH and acyl-CoAs in BsCoaA and the requirement of a monovalent cation in BsCoaX. Both gene disruptants appeared to grow in a manner similar to the wild-type strain. With the BsCoaX disruptant, the BsCoaA had the ability to completely fill the intracellular CoA pool, whereas the BsCoaA disruptant did not. These findings clearly indicate that these 2 CoaAs are employed together in the CoA biosynthetic pathway in B. subtilis and that the contribution of the type I CoaA (BsCoaA) to the formation of the intracellular CoA pool is larger than that of the type III CoaA (BsCoaX).

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