STRUCTURAL-ANALYSIS OF INOSITOL PHOSPHOLIPIDS FROM TRYPANOSOMA-CRUZI EPIMASTIGOTE FORMS

Inositol phospholipids (IPL) from epimastigote forms of Trypanosoma cr uzi have been investigated by metabolic labelling with [H-3]palmitic a cid and by GLC-MS analysis of the lipids obtained from non-labelled pa rasites. The IPL fraction was separated into phosphatidylinositol (PI) and inositol-phosphoceramide subfractions, the latter accounting for 80-85% of the total IPL. The neutral lipids released from the IPLs by PI-specific phospholipase C (PI-PLC) from Bacillus thuringiensis were analysed by silica-gel and reverse-phase TLC for the radioactive lipid s and by GLC-MS for the non-radioactive samples. Ceramides containing dihydrosphingosine and sphingosine with C-16:0 and C-18:0 fatty acids were identified. The main component in the [3H]palmitic acid-labelled ceramides was palmitoyldihydrosphingosine, while in the non-labelled s ample the ceramides contained mainly sphingosine. This could reflect p artial uptake of phospholipid from the medium. The PI contain both alk ylacyl-and diacyl-glycerol lipids, with the ether lipid being more abu ndant. The latter was identified as 1-O-hexadecylglycerol esterified b y C-18:2 and C-18:1 fatty acids. Interestingly, the same lipid had bee n identified in the anchor of the 1G7 glycoprotein of T. cruzi metacyc lic forms.