Heterogeneity in the Biosynthesis of Mucin O-Glycans from Trypanosoma cruzi Tulahuen Strain with the Expression of Novel Galactofuranosyl-Containing Oligosaccharides

Abstract

Sialoglycoprotein from Trypanosoma cruzi strains participates in important biological functions in which the O-linked glycans play a pivotal role, and their structural diversity may be related to the parasite's virulence pattern. To provide supporting evidence for this idea, we have determined the structure of novel linear and branched alpha-O-GlcNAc-linked oligosaccharides present on the mucins of the T. cruzi Tulahuen strain. The O-glycans were isolated as oligosaccharide alditols by reductive beta-elimination, purified, and characterized by nuclear magnetic resonance spectroscopy and methylation analysis. Two core families were synthesized by the parasite: the Galfbeta1-->4GlcNAc and Galpbeta1-->4GlcNAc. The Galfbeta1-->4GlcNAc core yields three series of O-chain structures. In the first, the Galf residue is nonsubstituted, while in the other series it is elongated by the activity of galactopyranosyl or galactofuranosyl transferases giving rise to Galp-beta-(1-->2)-Galf-beta-(1-->4) or Galf-beta-(1-->2)-Galf-beta-(1-->4) substructures not previously observed. The three series can arise by further galactopyranosylation of the GlcNAc O-6 arm. Sialylation was the only observed elaboration of the Galpbeta1-->4GlcNAc core family. Thus the determination of the structures of the O-glycans from T. cruzi Tulahuen mucins confirms the strain specificity of the glycosylation and predicts a relationship between it and parasite pathogenicity and the epidemiology of Chagas' disease.

Synthesis of galactofuranose-containing disaccharides using thioimidoyl-type donors

“…[6][7][8][9][10][11][12][13][14][15] Among hexoses present in a furanose form, three nat- 33 or to galactofuranosyl entities. 29,34,35,23 Among these natural products, most of the Galf units are connected with their aglycon through b-D D- (1!6) or b-D D-(1!5) linkages (Table 1).…”

Methylation-GC-MS analysis of arabinofuranose- and galactofuranose-containing structures: rapid synthesis of partially O-methylated alditol acetate standards

“…Units of Araf are found in polysaccharides of plants, as in gums and free or protein-linked arabinogalactans: to the latter many functions have been assigned, including plant growth and development, as well as cell proliferation, expansion and death (Svetek et al 1999). On the other hand, galactofuranosyl-containing molecules do not occur in green plants, but are widespread in glycolipids, proteoglycans, cell-wall polysaccharides, and exopolysaccharides (EPS) of fungi and yeasts (Barreto-Bergter and Gorin 1983, Levery et al 1998, Sassaki et al 2002, Jones et al 2004. Galf units are also present in macromolecules of bacteria and protozoans, but not in mammals, which are highly immunogenic to them.…”

Synthesis of 2,3,5,6-tetra-O-benzyl-D-galactofuranose for α-glycosidation

“…Two enzymes are required for Galf incorporation to glycoconjugates, a low efficiency mutase that transform UDP-Galp to UDPGalf, 6 and a recently described, UDP-Galf transferase, 7 which transfers the Galf unit to the sugar chain. β-Galactofuranosyl units are commonly found in Mycobacterium tuberculosis, 8 Leishmania, 9 and Trypanosoma cruzi 10 as examples. However, there are only few reported examples in which galactofuranose occurs in the alpha configuration.…”