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

摘要

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 Galalpha3GalNAcbeta4[PC6]GlcNAcbeta3Manbeta4Glc and Galalpha3GalNAcbeta4[PC6]GlcNAcbeta3[PE6]Manbeta4Glc, 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, H-1- and C-13-NMR spectroscopy, exoglycosidase cleavage and electrospray ionization ion-trap MS. The extended components comprised novel. structural motifs such as di-substituted alpha-galactose carrying two beta-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.