FIGURE 5.

Effect of succinyl acetone on T. gondii. A, inhibition of PBGS activity, assayed as porphobilinogen production by T. gondii tachyzoite lysates (preincubated 20 min with inhibitor in 100 mm Bistris propane buffer, pH 9.0, at 37 °C prior to 1-h incubation with substrate). B, inhibition of heme biosynthesis, assayed as ¹⁴C-ALA incorporation into heme by extracellular tachyzoite stage parasites. C, inhibition of T. gondii growth by succinylacetone. Transgenic parasite tachyzoites expressing luciferase (circles) were used to monitor growth in primary human foreskin fibrobast cells. Shading indicates positive and negative controls. Squares, untreated parasites; triangles, parasites lacking the luciferase transgene. Error bars indicate standard deviation.