Abstract

Summary Plasmodium parasites possess a single pyruvate dehydrogenase (PDH) enzyme complex that is localized to the plastid-like organelle known as the apicoplast. Unlike most eukaryotes, Plasmodium lacks a mitochondrial PDH. The PDH complex catalyzes the conversion of pyruvate to acetyl-CoA, an important precursor for the tricarboxylic acid cycle and type II fatty acid synthesis (FAS II). In this study, using a rodent malaria model, we show that the PDH E1alpha and E3 subunits co-localize with the FAS II enzyme FabI in the apicoplast of liver stages but are not significantly expressed in blood stages. Deletion of the E1alpha or E3 subunit genes of P. yoelii PDH caused no defect in blood stage development, mosquito stage development or early liver stage development. However, the gene deletions completely blocked the ability of the e1alpha(-) and e3(-) parasites to form exo-erythrocytic merozoites during late liver stage development, thus preventing the initiation of a blood stage infection. This phenotype is similar to that observed for deletions of genes involved in FAS II elongation. The data strongly support the hypothesis that the sole role of PDH is to provide acetyl-CoA for FAS II.