Reinvestigation of the carbohydrate chains of calf fetuin using 13C-n.m.r. spectroscopy.
The triantennary structure of the N-linked oligosaccharide side-chain of fetuin, elucidated by a combination of 13C-n.m.r. spectroscopy and enzymic degradations, accords with that reported earlier with respect to the branching pattern, but the ratio of the N-acetylneuraminic acid linkages to the galactose residues [alpha-(2----3) vs. alpha-(2----6)] was found to be 1:1, indicating structural heterogeneity of the side chains. Also, one out of nine galactosyl residues is linked to 2-acetamido-2-deoxy-beta-D-glucose by a (1----3) rather than a (1----4) linkage. The chemical shifts reported are in excellent agreement with those for the intact glycoprotein. Unusual chemical shift effects lead to the conclusion that the alpha-NeuAc-(2----6) residues interact with other parts of the oligosaccharide side-chain. The action of beta-D-galactosidase from Aspergillus niger on desialylated fetuin removed approximately 85% of the beta-Gal residues (1----4)-linked to GlcNAc and 65% of the beta-Gal residues (1----3)-linked to GalNAc, but none of the beta-Gal residues (1----3)-linked to GlcNAc.
D000818:Animals; D002236:Carbohydrate Conformation; D002240:Carbohydrate Sequence; D002241:Carbohydrates / Q000032:analysis; D002417:Cattle; D006020:Glycopeptides / Q000032:analysis; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D000509:alpha-Fetoproteins; D001616:beta-Galactosidase
D002241:Carbohydrates; D006020:Glycopeptides; D000509:alpha-Fetoproteins; D001616:beta-Galactosidase