Mechanism of Action of -Acyl and -Alkoxy Fosmidomycin Analogs: Mono- and Bisubstrate Inhibition of IspC from , a Causative Agent of Malaria.

Malaria is a global health threat that requires immediate attention. Malaria is caused by the protozoan parasite , the most severe form of which is . The methylerythritol phosphate (MEP) pathway of isoprenoid biosynthesis is essential to the survival of many human pathogens, including , but is absent in humans, and thus shows promise as a new antimalarial drug target. The enzyme 1-deoxy-d-xylulose 5-phosphate reductoisomerase (IspC) catalyzes the first committed step in the MEP pathway. In addition to a divalent cation (Mg), the enzyme requires the substrates 1-deoxy-D-xylulose 5-phosphate (DXP) and NADPH to catalyze its reaction. We designed -alkoxy and acyl fosmidomycin analogs to inhibit the activity of IspC in a bisubstrate manner. Enzyme assays reveal that the -alkoxy fosmidomycin analogs have a competitive mode of inhibition relative to both the DXP- and NADPH-binding sites, confirming a bisubstrate mode of inhibition. In contrast, the -acyl fosmidomycin analogs demonstrate competitive inhibition with respect to DXP but uncompetitive inhibition with respect to NADPH, indicating monosubstrate inhibitory activity. Our results will have a positive impact on the discovery of novel antimalarial drugs.