Phosphopantothenoylcysteine Decarboxylase (PPCDC)

Biosynthesis of coenzyme A (CoA) from pantothenic acid (vitamin B5) is an essential universal pathway in prokaryotes and eukaryotes. PPCDC (EC 4.1.1.36), one of the last enzymes in this pathway, converts phosphopantothenoylcysteine to 4-prime-phosphopantetheine. PPCDC functioned within the CoA synthetic pathway, and they verified PPCDC function by complementation in E. coli. Incubation of PPCS, PPCDC, and the bifunctional enzyme COASY with the necessary substrates and cofactors reconstituted the 4-step biochemical transformation of phosphopantothenate to CoA. Saccharomyces cerevisiae Hal3 and Vhs3 are moonlighting proteins, forming an atypical heterotrimeric decarboxylase (PPCDC) required for CoA biosynthesis, and regulating cation homeostasis by inhibition of the Ppz1 phosphatase.