STRUCTURAL CHARACTERIZATION OF NOVEL OLIGOSACCHARIDES OF CELL-SURFACEGLYCOPROTEINS OF TRYPANOSOMA-CRUZI

Affinity-purified glycopeptides were prepared from Trypanosoma cruzi u sing the carbohydrate-specific monoclonal antibody WIC29.26, These gly copeptides contain rhamnose, fucose, xylose, and galactose, in the rat io 1:1:2:3, A series of oligosaccharides was released from the glycope ptides by mild acid hydrolysis, while, in contrast, no oligosaccharide s were released by either peptide N-glycosidase F or conventional base -catalyzed beta-elimination and reduction, This suggested the presence of a phosphodiester linkage between the carbohydrate and peptide, whi ch was further supported by the detection of phosphothreonine in the g lycopeptides, The mild acid liberated (MAL) fraction was resolved into two major acidic oligosaccharides (MAL-P1 and MAL-P2), two minor neut ral oligosaccharides (MAL-P1b and MAL-P2b) and a neutral fraction (MAL -N1), consisting of Gal and Xyl monosaccharides, The MAL-P1 and MAL-P2 oligosaccharides proved to be hexa- and heptasaccharides that shared a common xylose reducing terminus, but differed by one galactofuranose residue, and their negative charge was shown to be due to the presenc e of cyclic-phosphate attached to nonreducing terminal galactofuranose residues, The MAL-P1b and MAL-P2b oligosaccharides appeared to be non phosphorylated versions of MAL-P1 and MAL-P2. Partial structures of MA L-P1 and MAL-P2 are suggested, based on compositional analyses, electr ospray mass spectrometry, and tandem mass spectrometry before and afte r permethylation. The origin and significance of these unique trypanos omatid glycoconjugates is discussed.