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

Abstract

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 (1)H-(1)H and (1)H-(13)C 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: HSO(3)(4)(GalNAcbeta 1-4GlcNAcbeta 1-3)(1-3)GalNAcbeta 1-4(GlcNAcbeta 1-3)(0-1)GlcNAcbeta 1-6GalNAc-ol.

O-Linked N,N′-Diacetyllactosamine (LacdiNAc)-modified Glycans in Extracellular Matrix Glycoproteins Are Specifically Phosphorylated at Subterminal N-Acetylglucosamine

“…There are only few reports on other LacdiNAc-modified O-glycoproteins. Among these, the oviductal mucins from Triturus alpestris (14) and cercarial glycoproteins from Schistosoma mansoni (15) have to be mentioned. Here, we provide evidence for the specific expression of LacdiNAc-terminating O-linked glycans on six extracellular matrix glycoproteins or membrane-tethered glycoproteins that fulfill functions by interacting with the extracellular matrix (ECM) network, like ␣-dystroglycan.…”