Characterization of asparagine-linked oligosaccharides on a mouse submandibular mucin

The asparagine-linked oligosaccharides from an adult female mouse submandibular gland mucin were released by treatment with peptide-N4-(N-acetyl-beta-glucosaminyl)asparagine amidase F or endo-beta-N-acetylglucosaminidase H. Endo-beta-N-acetylglucosaminidase H appeared to be more effective at releasing the asparagine-linked oligosaccharides from this mucin than was peptide-N4-(N-acetyl-beta-glucosaminyl)-asparagine amidase F. After quantitative reductive labelling with the fluorophore, 8-aminonaphthalene-1,3,6-sulphonic acid, the oligosaccharides were separated by polyacrylamide gel electrophoresis and isolated. The individual oligosaccharides were sequenced by a battery of recombinant exoglycosidases. Approximately 50% of the oligosaccharides were of the high-mannose type. The five-mannose member of this family was the most prevalent. The second group of oligosaccharides were of the non-bisected hybrid type. No complex asparagine-linked oligosaccharides were detected. The hybrids exhibited both biantennary and triantennary branching patterns. The triantennary hybrid was the most common hybrid at > 30% of all oligosaccharides. With approximately 98% of the hybrid oligosaccharides sialylated and all lacking a bisecting N-acetylglucosamine, these oligosaccharides as a group have been only rarely observed in other glycoproteins. The fully sialylated triantennary hybrid may be unique.