Uptake and kinetic properties of choline and ethanolamine in Plasmodium falciparum

RESUMO

Purpose: The asexual proliferation of Plasmodium; inside the erythrocyte; is accompanied by the synthesis of huge quantities of phosphatidylcholine (PtdCho) and phospha- tidylethanolamine (PtdEtn). These needful phospholipids for the cytoplasmic membrane of the merozoites are provided by the precursors choline and ethanolamine. PtdCho and PtdEtn are synthesized by the parasite because the erythrocyte is unable to do it. In order to assess the dynamism of the phospholipid pathways; we aimed to inves- tigate the respective shape of the uptake of choline and ethanolamine by Plasmodium falciparum. Method: Time-course experiments and kinetic assays were performed respectively with fixed and ranged concentrations of radioactively-labelled choline and ethanolamine. The labelled-precursors were added in the culture of P. falciparum infected-erythrocytes and the incorporated molecules in phospholipids were measured with a scintigraph counter. Result: The results showed that the incorpo- ration of precursors in the infected-erythrocyte occurred with a Michaelis-Menten's kinetic shape. According to the maximum rate (Vmax); the pathway of ethanolamine incorpo- ration was faster than that of choline. Similarly; affinity for ethanolamine was greater than that of choline. Conclusion: Although PtdCho is the major phospholipid in the membrane; this study rules out that the influx of ethanolamine in the infected-erythrocyte; in vivo conditions; is more dynamic than choline