Phospholipid Biosynthesis in Synchronous Plasmodium falciparum Cultures1

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Abstract
The metabolism of phospholipids in synchronous P. falciparum-infected erythrocytes [from humans] was studied over one cycle of 48 h by the incorporation of labeled palmitate, serine, choline and myoinositol into cellular lipids. The rates of incorporation of palmitate and serine into total phospholipids and of choline into phosphatidylcholine (PC) were linear with the maturation of the parasite, increasing by a factor of 2-5.6 according to the precursors. The rate of inositol incorporation into phosphatidylinositol was 9.6 times higher at the schizont stage than at the ring stage, with a marked increase in the 2nd half of the cycle. A significant incorporation of palmitate into triglycerides also occurred during the schizont stage of the parasite. The incorporations of serine and palmitate into phosphatidylethanolamine (PE) and PC showed a net increase at .apprx. the 20th h of the cycle, while the radioactivities recovered in phosphatidylserine (PS) had already reached a maximum by this time. An instantaneous transformation of PS into PE and PC through a decarboxylation of PS into PE, then a methylation of PE into PC was indicated during the 2nd half of the cycle. Although PS is a minor component of the Plasmodium parasite, the important role of this phospholipid as a precursor of PE and PC, which are major constituents of parasite phospholipids was shown.