Chondroitinase ABC digestion of dermatan sulphate. N.m.r. spectroscopic characterization of the oligo- and poly-saccharides

Abstract

Dermatan sulphates, in which iduronate was the predominant uronate constituent, were partially digested by chondroitinase ABC to produce oligosaccharides of the following structure: .DELTA.UA-[GalNAc(4SO3)-IdoA]mGalNAc(4SO3) [where m = 0-5, .DELTA.UA represents .beta.-D-gluco-4-enepyranosyluronate, IdoA represents .alpha.-L-iduronate and GalNAc(4SO3) represents 2-acetamido-2-deozy-.beta.-D-galactose 4-O-sulphate], which were fractionated by gel-permeation chromatography and examined by 100 MHz 13C-n.m.r. and 400/500 MHz 1H-n.m.r. spectroscopy. Experimental conditions were established for the removal of non-reducing terminal unsaturated uronate residues by treatment with HgCl2, and reducing terminal N-acetylgalactosamine residues of the oligosaccharides were reduced with alkaline borohydride. These modifications were shown by 13C-n.m.r. spectroscopy to have proceeded to completion. Assignments of both 13C-n.m.r. and 1H-n.m.r. resonances are reported for the GalNAc(4SO3)-IdoA repeat sequence in the oligosaccharides as well as for the terminal residues resulting from enzyme digestion and subsequent modifications. A full analysis of a trisaccharide derived from dermatan sulphate led to the amendment of published 13C-n.m.r. chemical-shift assignments for the polymer.