A novel isotopic labeling approach reveals adaptability in TCA reactions of Plasmodium falciparum

Abstract

Malaria, an infectious disease caused by parasites of the genus Plasmodium, kills more than a million people each year. As parasite strains resistant to all known antimalarials emerge, new drugs are badly needed. The search for new antimalarials will require a greater understanding of parasite metabolism. To help attain this understanding, I helped develop and validate a new stable isotope-labeling technique, called multi-channel labeling, which takes advantage of the parasite’s streamlined metabolic network to simultaneously label multiple central carbon metabolism pathways in the same experiment. This new technique was used in experiments investigating parasite metabolism in a variety of drug and genetic conditions, with an eye towards explaining the recently-discovered nonessentiality of most tricarboxylic acid cycle (TCA) enzymes. The results of these experiments support a model for parasite survival with TCA deletions in which flux through remaining TCA reactions increases to drive the mitochondrial membrane potential. These results also demonstrate that extracellular aspartate is excluded from the parasite’s de novo pyrimidine synthesis and purine salvage pathways, suggesting a role for substrate channeling or compartmentalization in these critical reactions.