TRYPANOSOMA-CRUZI - NITROGENOUS-BASE-CONTAINING PHOSPHATIDES IN TRYPOMASTIGOTE FORMS - ISOLATION AND CHEMICAL-ANALYSIS

In trypanosomatids, little is known about the biosynthetic pathways in volved in the metabolism of ethanolamine. In an attempt to clarify thi s point, an exhaustive analysis of the chloroform:methanol extract of T. cruzi trypomastigotes metabolically labeled with [C-14]ethanolamine , in comparison with the lipids from [H-3]palmitic acid-incorporated p arasites, was performed. In both cases, phosphatidylethanolamine and l ysophosphatidylethanolamine were detected, while phosphatidylcholine a nd lysophosphatidylcholine were only labeled with the fatty acid precu rsor. However, dimethylphosphatidylethanolamine was isolated from para sites labeled with the base precursor, indicating the ability of trypa nosomes to methylate phosphatidylethanolamine to dimethylphosphatidyle thanolamine. Fatty acids of the labeled phospholipids were analyzed by reverse-phase thin-layer chromatography and fluorography. Interesting ly, phospholipids from the trypomastigote stage show palmitic acid (C1 6:0) and stearic acid (C18:0) as the only labeled components. The same saturated fatty acids were found free and as components of the radioa ctive triglycerides. No unsaturated fatty acids were detected, in acco rdance with the results obtained with inositolphospholipids. Conversel y, when the fatty acids of phospholipids purified from nonlabeled para sites were analyzed by gas-liquid chromatography and gas-liquid chroma tography-mass spectrometry, C18:1 was also detected. A striking findin g was the presence of a considerable amount of free lignoceric acid (C 24:0). Also, the C24:0 fatty acid was identified in the triglyceride f raction and as a component of phosphatidylcholine. The limited capacit y of trypomastigote forms to elongate fatty acids was determined. In c ontrast with the results reported for other noninfective forms of the parasite, the absence of unsaturated fatty acids due to a low activity of desaturases was observed. (C) 1997 Academic Press.