Investigations on Pantothenic Acid and Its Related Compounds: IX. Biochemical Studies (4).* Separation and Substrate Specificity of Pantothenate Kinase and Phosphopantothenoylcysteine Synthetase**

Abstract

1. To investigate the pathway of biosynthesis of Co A in rat liver, pantothenate kinase [EC 2.7.1.33] and phosphopantothenoylcysteine synthetase [EC 6.3.2.5] have been completely separated from each other. 2. Based on the specificity of these two separate enzymes, it was suggested that pantothenate was first phosphorylated and then condensed with cysteine to form phosphopantothenoylcysteine in the course of CoA biosynthesis in rat liver. 3. It has been shown that rat-liver pantothenate kinase catalyzes the phosphorylation not only of pantothenate and panteth(e)ine but also of pantothenoylcyst(e)ine.