Specific conversion of D-galactose into D-galacturonic acid residues in glycoproteins: a facile method for carbohydrate linkage-analysis.
The terminal D-galactopyranosyl residues of asialoglycopeptides isolated from human alpha1-acid glycoprotein were oxidized in nearly quantitative yield to the corresponding uronic acid residues by a two-step sequence employing D-galactose oxidase followed by treatment with Tollens reagent, Ag(NH3)+2. Mild acid hydrolysis of the oxidized glycopeptides led to the isolation of the corresponding aldobiuronic acid(s). Structural and colorimetric analysis revealed that only one aldobiuronic acid 2-amino-2-deoxy-4-O-(beta-D-galactopyranosyluronic acid)-D-glucose, was isolated from the oxidized glycopeptides of alpha1-acid glycoprotein. This method can readily distinguish between the (1 leads to 3), (1 leads to 4), and (1 leads to 6) isomers of the corresponding aldobiuronic acids.
D055598:Chemical Phenomena; D002621:Chemistry; D005690:Galactose; D006020:Glycopeptides / Q000032:analysis; D006801:Humans; D009961:Orosomucoid / Q000032:analysis*; D010084:Oxidation-Reduction; D014574:Uronic Acids
D006020:Glycopeptides; D009961:Orosomucoid; D014574:Uronic Acids; D005690:Galactose