Isolation and Characterization of Oligosaccharides from Canine Submaxillary Mucin

Pure mucin isolated from canine submaxillary glands was treated with alkaline borohydride and products of degradation were fractionated by a procedure that included ion-exchange chromatography, gel filtration, high-voltage electrophoresis and paper chromatography. Seven acidic, reduced oligosaccharides were isolated being divided into two distinct types: one, containing sialic acid and no glucosamine or sulfate (type A) and the other containing glucosamine and sulfate but no sialic acid (type B). The most complete oligosaccharide of type A designated component (I) was a tetrasaccharide α-l-fucopyranosyl-(1 2)-d-galactopyranosyl-[N-acetylneuraminyl-(2 6)]-2-acetamido-2-deoxy-d-galactitol. The most complex oligosaccharide of type B designated component (V) has a hexasaccharide with the following structure: α-l-fucopyranosyl-(1 2)-β-d-galactopyranosyl-(1 3, 4, or 6)-β-2-acetamido-2-deoxy-d-glucopyranosyl 3 or 4 sulfate-(1 6)-α-l-fucopyranosyl-(1 2)]-β-d-galactopyranosyl-(1 3) 2-acetamido-2-deoxy-d-galactitol. All the other acidic isolated oligosaccharides were derived from these two main components. No oligosaccharide containing both sialic acid and glucosamine sulfate could be demonstrated. Based on these structural features, a possible biosynthetic pathway leading to the two different oligosaccharide chains is discussed. Variations in ratios of sugars observed in canine submaxillary mucin and especially the reciprocal relationship between sialic acid and fucose noted earlier (1962) by Dische, Pallavicini, Kavasaki, Smirnow, Cizek and Chien may reflect variations in the proportions of these two types of oligosaccharides.