Toxicity of myristic acid analogs toward African trypanosomes.

New drugs are needed for treatment of diseases caused by African trypanosomes. One possible target for chemotherapy is the biosynthesis of the glycosyl phosphatidyl-inositol (GPI) of this parasite's variant surface glycoprotein (VSG). Unlike mammalian GPIs, the diacylglycerol moiety of the VSG anchor contains only myristate (tetradecanoate), added in unique remodeling reactions. We previously found that 11-oxatetradecanoic acid [i.e., 10-(propoxy)decanoic acid] is selectively toxic to trypanosomes. We have now assayed 244 different fatty acid analogs, most with chain lengths comparable to that of myristate, for trypanocidal effects. In these assays we surveyed the effects on toxicity of systematic alterations in the analogs' steric, conformational, and hydrophobic properties. We also used three 3H-labeled oxatetradecanoic acids to explore the mechanism of analog action. Their incorporation into VSG correlated roughly with toxicity, although they also were incorporated into phospholipids and other proteins. Myristate analogs are useful for studying the mechanism of GPI myristolyation, and they are candidates for antitrypanosomal chemotherapy.