The complete structure of the complex oligosaccharides of fetuin has been established. The three fractions of complex oligosaccharide which were isolated by ion exchange chromatography following pronase digestion (F-I, F-II, and F-III) had identical molar ratios of sialic acid (Sia), galactose, mannose, and N-acetylglucosamine of 3:3:3:5. A combination of methylation analyses, Smith periodate degradations, and endoglycosidase and exoglycosidase digestions were utilized to establish the structure. Features of this structure not previously established include the presence of 2 residues of α2,3- and 1 residue of α2,6-linked sialic acid and their location relative to the mannose branch points. Also unusual is the presence of an α-linked branch mannose with substituents at positions 2 and 4 which is in turn linked to position 6 of the β-linked, branch mannose. These features result in unexpected resistance to specific exoglycosidases.
|Number of pages||7|
|Journal||Journal of Biological Chemistry|
|State||Published - Jan 1 1979|