STRUCTURAL STUDIES ON THE HEXASACCHARIDE ALDITOLS ISOLATED FROM THE CARBOHYDRATE-PROTEIN LINKAGE REGION OF DERMATAN SULFATE PROTEOGLYCANS OF BOVINE AORTA - DEMONSTRATION OF IDURONIC ACID-CONTAPNING COMPONENTS

Five major hexasaccharide alditols were isolated from the carbohydrate -protein linkage region of bovine aorta dermatan sulfate peptidoglycan s after reductive beta-elimination and subsequent chondroitinase ABC d igestion. These molecules account for at least 55.3% of the total link age region. Their structures were analyzed by enzymatic digestion in c onjunction with high performance liquid chromatography, electrospray i onization mass spectrometry, and 500-MHz one- and two-dimensional H-1 NMR spectroscopy. Three of these compounds have the conventional hexas accharide core; Delta HexA alpha(1)-3Gal-NAc beta 1-4GlcA beta 1-3Gal beta 1-3Gal beta 1-4Xyl-ol. One is nonsulfated, and the other two are monosulfated on C6 or C4 of the GalNAc residue. They represent at leas t 6.3, 5.2, and 28.8% of the total linkage region, respectively. The o ther two compounds have the following hitherto unreported hexasacchari de core with an internal iduronic acid residue in common; Delta HexA a lpha 1-3-GalNac beta 1-4IdoA alpha 1-3Gal beta 1-3Gal beta 1-4Xyl-ol. One is monosulfated on C4 of the GalNAc, and the other is disulfated o n C4 of the GalNAc and of the galactose residue substituted by the idu ronic acid residue, These two compounds account for 35% of the five is olated hexasaccharide alditols and at least 4.3 and 10.7% of the total linkage region, respectively. The latter two structures form a striki ng contrast to the currently accepted conception that heparin, heparan sulfate, and chondroitin/dermatan sulfate share the common linkage te trasaccharide core GlcA beta 1-3Gal beta 1-3Gal beta 1-4Xyl. The biolo gical significance of the isolated structures is discussed in relation to the biological functions and the biosynthetic mechanisms of dermat an sulfate.