The nematode Caenorhabditis elegans synthesizes unusual O-linked glycans: identification of glucose-substituted mucin-type O-glycans and short chondroitin-like oligosaccharides

The free-living nematode Caenorhabditis elegans is a relevant model for stu dies on the role of glycoconjugates during development of multicellular org anisms. Several genes coding for glycosyltransferases involved in the synth esis of N- and O-linked glycans have already been isolated, but, apart from repetitive dimers of glycosaminoglycans, no detailed structure of either t ype of component has been published so far. This study aimed to establish t he structures of the major O-glycans synthesized by C. Elegans to give an i nsight into the endogenous glycosyltransferase activities expressed in this organism. By the use of NMR and MS, we have resolved the sequence of seven of these components that present very unusual features, Most of them were characterized by the type-1 core substituted on Gal and/or GalNAc by (beta1 -4)Glc and (beta1-6)Glc residues. Another compound exhibited the GalNAc(bet a1-4)N-acetylglucosaminitol sequence in the terminal position, to which was attached a tetramer of beta -Gal substituted by both Fuc and 2-O-methyl-fu cose residues. Our experimental procedure led also to the isolation of glyc osaminoglycan-like components acid oligomannosyl-type N-glycans. In particu lar, the data confirmed that C. elegans synthesizes the ubiquitous linker s equence GlcA(beta1-3)Gal(beta1-3)Gal(beta1-4)Xyl.