Structural features of the lipopeptidophosphoglycan from Trypanosoma cruzi common with the glycophosphatidylinositol anchors.

The lipopeptidophosphoglycan (LPPG) from Trypanosoma cruzi, a major constituent of the plasma membrane of epimastigote forms, has been now extracted with butanol/water from delipidated cells and purified by hydrophobic chromatography. We have found that the LPPG undergoes two reactions, characteristic of the glycosylphosphatidylinositol anchors: (a) cleavage of the ceramide by phosphatidylinositol-specific phospholipase C (PtdIns-specific phospholipase C) from Bacillus thuringiensis, (b) nitrous acid deamination of the non-N-acylated glucosamine. Palmitoylsphinganine, palmitoylsphingosine, lignoceroylsphinganine and, as minor components, the stearoylceramides were identified by gas liquid chromatography/mass spectrometry. The presence of cross reacting determinant (CRD) epitopes in the glycophosphoinositol released by PtdIns-specific phospholipase C was investigated by direct and inhibition ELISA. A sample of glycophosphoinositol containing 5 micrograms carbohydrate caused 60% inhibition of the binding of anti-CRD antibodies raised against the soluble form of variant surface glycoprotein.