Structure elucidation of NeuAc, NeuGc and Kdn-containing O-glycans released from Triturus alpestris oviductal mucins

Eggs from Amphibia are surrounded by several layers of jelly that are needed for proper fertilization. Jelly coat is composed of highly glycosylated mucin-type glycoproteins containing up to 60% of carbohydrates, which display a remarkable species-specificity. This material obtained from Triturus alpestris was submitted to reductive beta -elimination and the released oligosaccharide-alditols were further fractionated by HPLC. Structural characterization was performed through a combination of two dimensional H-1-H-1 and H-1-C-13 NMR and ESI-MS/MS analysis. Numerous carbohydrate chains are characterized by the presence of the Cad (Sd(a)) determinant, including respectively NeuAc, NeuGc or Kdn as a sialic acid. But the most significant O-glycan sequences which mark the difference between the jelly of T. alpestris and other studies amphibian jellies are polymers of GalNAc(beta 1-4)GlcNAc (LacdiNAc) which form part of the following sequence: HSO3(4)(GalNAc beta 1-4GlcNAc beta 1-3)(1-3)GalNAc beta 1-4(GlcNAc beta 1-3)(0-1)GlcNAc beta 1-6GalNAc-ol.