Metabolic Activation versus Masked Prodrugs: Bisubstrate Mimic Inhibitors of CoaBC's PPCS Activity in Mycobacterium...

The bifunctional bacterial CoaBC is a coenzyme A (CoA) biosynthetic protein that serves as a validated bactericidal target in Mycobacterium tuberculosis (Mtb). In Staphylococcus aureus, it is the target of the natural product antibiotic CJ-15,801, which inhibits its phosphopantothenoylcysteine synthetase (PPCS) activity by forming a bisubstrate mimic of its reactive reaction intermediate in situ after metabolic activation by pantothenate kinase, the first CoA biosynthetic enzyme. We prepared PPCS bisubstrate mimics with various stable linkers that would also require metabolic activation and used purified Mtb and S. aureus enzymes to evaluate their inhibition. Additionally, we prepared masked prodrug versions of the phosphorylated (activated) form of CJ-15,801 and tested these and the bisubstrate mimics, as whole-cell inhibitors of Mtb and S. aureus. We demonstrate that such inhibitors hold promise for the development of antimicrobials targeting these organisms, although further structure-activity relationship studies are necessary to address current challenges and improve their potency.