Abstract
Malaria is caused by the infection and destruction of red blood cells by protozoan parasitesbelonging to the genus Plasmodium. During its intra-erythrocytic development, Plasmodiumfalciparum requires massive biosynthesis of membranes which are mainly composed of phospholipids.Phosphatidylcholine (PC) and phosphatidylethanolamine (PE) together represent about 80% of thetotal membrane lipids and inhibition of their biosynthesis leads to parasite death. PC and PE aresynthesized by the parasite's machinery mainly through the de novo CDP-choline and CDPethanolamine(Kennedy) pathways using respectively choline and ethanolamine as precursors. Thisstudy focuses on the rate limiting steps of these pathways catalyzed by CTP:phosphocholine andCTP:phosphoethanolamine cytidylytransferases (PfCCT and PfECT, respectively). In Plasmodiumspecies, both CCT and ECT contain two catalytic cores (CT domains) separated by a long linker.Interestingly, for CCT this feature is found only in three organisms, all from the phylum ofApicomplexa: Babesia, Theileria and Plasmodium, whereas the presence of two CT domains is ageneral feature in all ECTs known so far. The first part of this work consists in the biochemicalcharacterization of PfCCT and the investigation of its druggability. We showed that both PfCCT CTdomains are active and display similar kinetic parameters while only the N-terminal CT domain wasactive in PfECT. Subsequent to an in silico structure-based screening of compounds libraries, weidentified a PfCCT inhibitor able to inhibit PC synthesis as well as P. falciparum growth in vitro in thehigh µM range. This compound represents a first step toward the optimization of future more potentcompounds. In the second part of this study, we investigated the catalytic mechanism of PfECT anddeciphered its interactions with its ligands using biochemical, biophysical and structural approaches.Collectively, these results bring new insights into the biochemical and structural properties of thesetwo keys enzymes of the phospholipid metabolism in P. falciparum and pave the way for their futuredevelopment as potential drug target.