Figure 2.

Triclosan inhibits Plasmodium DHFR in vitro. (A) DHFR catalyzes the reduction of dihydrofolate (DHF) to tetrahydrofolate (THF), coupled with the oxidation of nicotinamide adenine dinucleotide phosphate (NADPH). This reaction was followed for HsDHFR and PvDHFR in the absence (blue) or presence (red) of 100 µM Triclosan at 340 nm. (B) Initial rates of reaction were determined and used to derive IC₅₀ values, with the standard deviation calculated from multiple kinetic runs (n = 3). To deal with variations in enzyme activity in different preparations, kinetic data were normalized as relative activities and fitted to % activity = % activity_max/(1 + [triclosan]/IC₅₀). Reaction conditions: [triclosan] = 0–200 μM, [HsDHFR] = 30.5 nM, [PvDHFR] = 18.5 nM, [Tris/HCl] = 0.1 M, pH 7.4, [DHF] = [NADPH] = 100 μM, 21 °C.