Phosphopantothenoylcysteine synthetase from Escherichia coli - Identification and characterization of the last unidentified coenzyme A biosynthetic enzyme in bacteria

Phosphopantothenoylcysteine synthase catalyzes the formation of (R) 4'-phos pho-N-pantothenoylcysteine from 4'-phosphopantothenate and L-cysteine: this enzyme, involved in the biosynthesis of coenzyme A (CoA), has not previous ly been identified. Recently it was shown that the NH2-terminal domain of t he Dfp protein from bacteria catalyzes the next step in CoA biosynthesis, t he decarboxylation of (R) 4'-phospho-N-pantothenoylcysteine to form 4'-phos phopantetheine (Kupke, T., Uebele, M,, Schmid, D., Jung, G,, Blaesse, M., a nd Steinbacher, S. (2000) J. Biol. Chem. 275, 31838-31846), We have partial ly purified phosphopantothenoylcysteine decarboxylase from Escherichia coli and demonstrated that the protein encoded by the dfp gene, here renamed co aBC, also has phosphopantothenoylcysteine synthetase activity, using CTP ra ther than ATP as the activating nucleoside 5'-triphosphate, This discovery completes the identification of all the enzymes involved in the biosynthesi s of coenzyme A in bacteria.