Structure determination of five sialylated trisaccharides with core types 1, 3 or 5 isolated from bovine submaxillary mucin

Abstract

In this study we have investigated the structures of five sialylated trisaccharides released from bovine submaxillary mucin by alkaline borohydride treatment and isolated by high-performance liquid chromatography. Three of the trisaccharides contained NeuAc while two contained NeuGc. One oligosaccharide contained core-type 1, two contained core-type 3 and two contained core-type 5. The structures, determined by a combination of one- and two-dimensional ¹H-NMR spectroscopy at 270 MHz and methylation analysis involving gas-liquid chromatography/mass spectrometry, were as follows: A4b, GalNAcα(1 → 3)[NeuAcα(2 → 6)]GalNAcol; A4c, GlcNAcβ(1 → 3)[NeuAcα(2 → 6)]GalNAcol; A4d, Galβ(1 → 3)[NeuAcα(2 → 6)]GalNAcol; A4e, GalNAcα(1 → 3)-[NeuGcα(2 → 6)]GalNAcol; A4f, GlcNAcβ(1 → 3)[NeuGcα(2 → 6)]GalNAcol. The oligosaccharides occurred in the approximate molar ratios 1.0:12.0:0.3:0.2:2.0. This is the first report of oligosaccharides containing core-type 5 and of the occurrence of oligosaccharides A4b, A4e, and A4f in bovine submaxillary mucin. ¹H-NMR data for structure A4e, which is a novel structure, are presented for the first time.