Biosynthesis of lipids by kinetoplastid flagellates.

Crifhidia fasciculata, Crifhidia oncopelti, Crifhidia luciliae, Crithidia sp. from Arilus crisfafus, Crifhidia acanthocephali, Blastocrifhidia culicis, Leishmania tarenfolae, and Lepfomonas Zepfoglossi were grown under axenic conditions in chemically defined media, and their fatty acids were determined. Palmitic, stearic, and a Cl9 cyclopropane acid were the major saturated fatty acids. Oleic, linoleic, and ylinolenic were the major unsaturated fatty acids. ar-Linolenic acid could not be detected in any of these organisms. Monounsaturated fatty acids were synthesized by direct oxidative desaturation of the corresponding saturated acids, and polyunsaturated fatty acids were synthesized by progressive desaturation and chain elongation of the monoenoic acids. The major lipids of C. fasciculafa and C. oncopeltitriglycerides, sterol esters, phosphatidylcholine, phosphatidylinositol, and phosphatidylethanolamine -were identical. Phosphatidylethanolamine contained the bulk of the cyclopropane acid found in C. fasciculata. Ergosterol was the major sterol of Crithidia, Blastocrithidia, and Zeishmania species. Methionine served as a source of methyl groups for the biosynthesis of both ergosterol and the cyclopropane acid.