Structures of N-linked and O-linked oligosaccharides on proteoglycan monomer isolated from the Swarm rat...

Monomer proteoglycans isolated from the Swarm rat chondrosarcoma contain O- and N-glycosidically linked oligosaccharides. The O-glycosidically linked ones were released from the protein core by alkaline borohydride treatment. After removal of sialic acid, the resulting oligosaccharide alditols were converted to N-trifluoroacetyl derivatives by trifluoroacetolysis. The N-trifluoroacetylated oligosaccharide alditols show shorter retention time on gas-liquid chromatography, as permethylated derivatives, than the corresponding N-acetyl derivatives. The mass spectra of these new derivatives also give more structural information and provide definitive structures. Alkaline borohydride treatment of the proteoglycans also released N-glycosidically linked oligosaccharide-peptides. These were purified and analyzed by Smith degradation, trifluoroacetolysis, and chromium trioxide oxidation. The results indicate that more than 70% of the N-glycosidically linked oligosaccharides have the following structure: (formula, see text) with the Fuc present on only about 60% of the oligosaccharides.