title: Synthesis of the O-linked pentasaccharide in glycoproteins of Trypanosoma cruzi and selective sialylation by recombinant trans-sialidase.
abstract: The mucin-like glycoproteins of Trypanosoma cruzi have novel O-linked oligosaccharides that are acceptors of sialic acid in the trans-sialidase (TcTS) reaction. The transference of sialic acid from host glycoconjugates to the mucins is involved in infection and pathogenesis. The synthesis of the pentasaccharide, beta-D-Galp-(1-->2)-[beta-D-Galp-(1-->3)]-beta-D-Galp-(1-->6)-[beta-D-Galf-(1-->4)]-D-GlcpNAc and the corresponding alditol, previously isolated by reductive beta-elimination of the mucins, is described. The key step was the 6-O-glycosylation of a easily accessible derivative of beta-D-Galf-(1-->4)-D-GlcpNAc with a beta-D-Galp-(1-->2)-[beta-D-Galp-(1-->3)]-D-Galp donor using the trichloroacetimidate method. The beta-linkage was diastereoselectively obtained by the nitrile effect. The pentasaccharide is the major oligosaccharide in the mucins of T. cruzi, G strain and presents two terminal beta-D-Galp residues for possible sialylation by TcTS. A preparative sialylation reaction was performed with its benzyl glycoside and the sialylated product was isolated and characterized. NMR spectroscopic analysis showed that selective monosialylation occurred at the terminal (1-->3) linked galactopyranose.
authors.affiliation: CIHIDECAR, Departamento de Química Orgánica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Pabellón II, 1428 Buenos Aires, Argentina.
authors.forename: Verónica M
authors.initials: VM
authors.lastname: Mendoza
authors.forename: Rosalía
authors.initials: R
authors.lastname: Agusti
authors.forename: Carola
authors.initials: C
authors.lastname: Gallo-Rodriguez
authors.forename: Rosa M
authors.initials: RM
authors.lastname: de Lederkremer
mesh_terms: D000818:Animals; D002240:Carbohydrate Sequence; D006023:Glycoproteins / Q000378:metabolism*; D008969:Molecular Sequence Data; D009077:Mucins / Q000737:chemistry*; D009439:Neuraminidase / Q000378:metabolism*; D019906:Nuclear Magnetic Resonance, Biomolecular; D009844:Oligosaccharides / Q000138:chemical synthesis*; D011994:Recombinant Proteins / Q000378:metabolism; D014349:Trypanosoma cruzi / Q000737:chemistry
chemical_list: D006023:Glycoproteins; D009077:Mucins; D009844:Oligosaccharides; D011994:Recombinant Proteins; C069715:trans-sialidase; D009439:Neuraminidase