UNIT 17.22A Nitrous Acid Degradation of Glycosaminoglycans

Glycosaminoglycans (GAGs) are made up of disaccharide units that are distinguished from each other by the monosaccharide units of which they are composed and by the degree and position of sulfation. These disaccharide units represent the monomeric units of the GAG; thus, measurement of the disaccharide composition of a GAG represents the first step in the characterization of the polymer. In this unit, cleavage of the glycosidic bonds of the N-sulfated GlcN residues in heparin and heparan sulfate is described, in addition to cleavage of the bonds between the N-acetylated amino sugar residues in heparin, heparan sulfate, chondroitin sulfate, dermatan sulfate, and keratan sulfate, and hyaluronic acid. Using these procedures involving, all GAGs can be converted completely to their constituent disaccharides and reduced with NaB[³H]₄) to yield labeled disaccharides that can be assayed qualitatively or quantitatively. The procedure may also be used to analyze metabolically labeled GAGs (with or without the use of NaB[³H]₄).