FULL PAPER Parasitology Babesia bovis Dihydroorotate Dehydrogenase (BboDHODH) is a Novel Molecular Target of Drug for Bovine Babesiosis

ABSTRACT. The emergence of drug resistance and adverse side effects of current bovine babesiosis treatment suggest that the search of new drug targets and development of safer and effective compounds are required. This study focuses on dihydroorotate dehydrogenase (DHODH), the fourth enzyme of pyrimidine biosynthesis pathway as a potential drug target for bovine babesiosis. Recombinant Babesia bovis DHODH protein (rBboDHODH) was produced in Escherichia coli and used for characterization and measurement of enzymatic activity. Furthermore, the effects of DHODH inhibitors were evaluated in vitro. The recombinant B. bovis DHODH histidine fusion pro-tein (rBboDHODH) had 42.4-kDa molecular weight and exhibited a specific activity of 475.7 ± 245 Unit/mg, a Km = 276.2 µM for L-dihydroorotate and a Km = 94.41 µM for decylubiquinone. A 44-kDa band of native BboDHODH was detected by Western blot analysis and found in parasites mitochondria using a confocal microscope. Among DHODH inhibitors, atovaquone (ATV) and leflunomide (LFN) significantly inhibited the activity of rBboDHODH as well as the growth of B. bovis in vitro. The half maximal inhibitory concentration (IC50) of ATV and LFN was 2.38 ± 0.53 nM and 52.41 ± 11.47 µM, respectively. These results suggest that BboDHODH might be a novel target for development of new drug for treatment of B. bovis infection. KEY WORDS: atovaquone, Babesia bovis, chemotherapeutic target agent, dihydroorotate dehydrogenase, leflunomide. doi: 10.1292/jvms.13-0419; J. Vet. Med. Sci. 76(3): 323–330, 2014 Babesia bovis is an intra-erythrocytic apicomplexan para-site of Babesiidae family, which is considered as principa