Mechanistic Binding Insights for 1-deoxy-D-Xylulose-5-PhosphateSynthase, the Enzyme Catalyzing the First Reaction of Isoprenoid Biosynthesis in the Malaria-causing Protists, \u3cem\u3ePlasmodium falciparum\u3c/em\u3e and \u3cem\u3ePlasmodium vivax\u3c/em\u3e

We have successfully truncated and recombinantly-expressed 1-deoxy-D-xylulose-5-phosphate synthase (DXS) from both Plasmodium vivax and Plasmodium falciparum. We elucidated the order of substrate binding for both of these ThDP-dependent enzymes using steady-state kinetic analyses, dead-end inhibition, and intrinsic tryptophan fluorescence titrations. Both enzymes adhere to a random sequential mechanism with respect to binding of both substrates: pyruvate and D-glyceraldehyde-3-phosphate. These findings are in contrast to other ThDP-dependent enzymes, which exhibit classical ordered and/or ping-pong kinetic mechanisms. A better understanding of the kinetic mechanism for these two Plasmodial enzymes could aid in the development of novel DXS-specific inhibitors that might prove useful in treatment of malaria