Phosphopantothenoylcysteine Synthetase (PPCS)

Biosynthesis of coenzyme A (CoA) from pantothenic acid (vitamin B5) is an essential universal pathway in prokaryotes and eukaryotes. PPCS (EC 6.3.2.5), one of the last enzymes in this pathway, converts phosphopantothenate to phosphopantothenoylcysteine.

Daugherty et al. (2002) showed that recombinant PPCS functioned within the CoA synthetic pathway. PPCS used ATP for the activation of substrate in the ligation reaction 4 times more efficiently than CTP. Daugherty et al. (2002) verified the function of PPCS 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.