Structural elucidation of zwitterionic carbohydrates derived from glycosphingolipids of the porcine parasitic nematode Ascaris suum

Abstract

Carbohydrates substituted with phosphocholine (PC) and phosphoethanolamine (PE) were released from zwitterionic glycosphingolipids of the pig parasitic nematode Ascaris suum by treatment with endoglycoceramidase. Individual glycans were obtained by HPLC on porous graphitic carbon followed by high-pH anion-exchange chromatography. In addition to the known pentasaccharides Galα3GalNAcβ4[PC6]GlcNAcβ3Manβ4Glc and Galα3GalNAcβ4[PC6]GlcNAcβ3[PE6]Manβ4Glc, the corresponding tri- and tetra-saccharides, as well as components with elongated structures, could be identified by matrix-assisted laser-desorption ionization—time-of-flight MS, methylation analysis, 1H- and 13C-NMR spectroscopy, exoglycosidase cleavage and electrospray ionization ion-trap MS. The extended components comprised novel structural motifs such as di-substituted α-galactose carrying two β-linked galactosyl residues, which were found to bear, in part, further fucose, galactose, N-acetylgalactosamine and/or N-acetylglucosamine moieties. Furthermore, additional fucosylation of the PC-substituted N-acetylglucosamine and a non-terminal fucosyl motif were detected. In conclusion, this study contributes significant new information on the glycome of nematodes.