LEAD DISCOVERY OF INHIBITORS OF THE DIHYDROFOLATE-REDUCTASE DOMAIN OFPLASMODIUM-FALCIPARUM DIHYDROFOLATE REDUCTASE-THYMIDYLATE SYNTHASE

A three-dimensional structure model of the dihydrofolate reductase (DH FR) domain of the bifunctional DHFR-thymidylate synthase of Plasmodium falciparum was used as a basis for computational screening of commerc ially available compounds for candidate inhibitors. Compounds which ca n stably dock to the model with strong ionic hydrogen bonds via proton ation by an aspartic acid residue at the bottom of the active site wer e identified through docking simulation. Among compounds thus identifi ed, 21 were assayed for inhibitory activity towards the recombinant DH FR domain, Two compounds, 4,4,7,8-tetramethyl-s-triazino(1,2-a)benzimi dazole and Trp-P-a, inhibited the recombinant P. falciparum DHFR domai n with Ki values of 0.54 and 8.7 mu M, respectively. Kinetic analysis showed that these compounds competitively inhibited the enzyme with re spect to the substrate dihydrofolate. These findings support the valid ity of both the modeled structure and the docking results. Furthermore , these compounds serve as leads for developing new DHFR inhibitors, s ince their skeletal structures are different from any of known DHFR in hibitors. This paper also reveals a new biological activity of Trp-P-2 , a potent mutagen. (C) 1997 Academic Press.