Pyrimidine biosynthesis presents an attractive drug target in malaria parasites 
due to the absence of a pyrimidine salvage pathway. A set of compounds designed 
to inhibit the Plasmodium falciparum pyrimidine biosynthetic enzyme 
dihydroorotate dehydrogenase (PfDHODH) was synthesized. PfDHODH-specific 
inhibitors with low nanomolar binding affinities were identified that bind in 
the N-terminal hydrophobic channel of dihydroorotate dehydrogenase, the presumed 
site of ubiquinone binding during oxidation of dihydroorotate to orotate. These 
compounds also prevented growth of cultured parasites at low micromolar 
concentrations. Models that suggest the mode of inhibitor binding is based on 
shape complementarity, matching hydrophobic regions of inhibitor and enzyme, and 
interaction of inhibitors with amino acid residues F188, H185, and R265 are 
supported by mutagenesis data. These results further highlight PfDHODH as a 
promising new target for chemotherapeutic intervention in prevention of malaria 
and provide better understanding of the factors that determine specificity over 
human dihydroorotate dehydrogenase.