Abstract
Five major hexasaccharide alditols were isolated from the carbohydrate-protein linkage region of bovine aorta dermatan sulfate peptidoglycans after reductive beta-elimination and subsequent chondroitinase ABC digestion. These molecules account for at least 55.3% of the total linkage region. Their structures were analyzed by enzymatic digestion in conjunction with high performance liquid chromatography, electrospray ionization mass spectrometry, and 500-MHz one- and two-dimensional 1H NMR spectroscopy. Three of these compounds have the conventional hexasaccharide 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 least 6.3, 5.2, and 28.8% of the total linkage region, respectively. The other two compounds have the following hitherto unreported hexasaccharide core with an internal iduronic acid residue in common; delta HexA alpha 1-3GalNAc 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 on C4 of the GalNAc and of the galactose residue substituted by the iduronic acid residue. These two compounds account for 35% of the five isolated hexasaccharide alditols and at least 4.3 and 10.7% of the total linkage region, respectively. The latter two structures form a striking contrast to the currently accepted conception that heparin, heparan sulfate, and chondroitin/dermatan sulfate share the common linkage tetrasaccharide core GlcA beta 1-3Gal beta 1-3Gal beta 1-4Xyl. The biological significance of the isolated structures is discussed in relation to the biological functions and the biosynthetic mechanisms of dermatan sulfate.
Highlights
From the tDepartment of Biochemistry, Kobe Pharmaceutical University, Higashinada-ku, Kobe 658 and the 'IITokyo Research Institute of Seikagaku Corporation, Higashiyamato-shi, Tokyo 207, Japan
We isolated five major hexasaccharide alditols from the carbohydrate-protein linkage region of a peptidoglycan preparation of bovine aorta, which is assumed to contain dermatan sulfate chains derived from small proteoglycans such as decorin and biglycan [27,28,29] in addition to those from large proteoglycans [30]
Since the discovery of the unique common carbohydrate sequence in the linkage region of various sulfated glycosaminoglycans including heparin, heparan sulfate, chondroitin sulfate, and dermatan sulfate, it has been accepted that the innermost uronic acid residue immediately adjacent to the linkage trisaccharide sequence of these glycosaminoglycan chains is glucuronic acid [10, 11]
Summary
IdoA, iduronic acid; HexA, hexuronic acid; ilHexA or il4 5HexA, 4-deoxy-a-L-threo-hex-4-enepyranosyluronic acid; ilDi-OS, il4,5HexAa(I-3)GalNAc; ilDi-6S, il4,5HexAa(I-3)GalNAc(6-sulfate); ilDi-4S, il4,5HexAa(I-3)GalNAc(4-sulfate); ilDi-diSD , il4,5HexA(2-sulfate)a( 1-3 )GalNAc(6-sulfate); ilDi-diSB , il4,5HexA(2-sulfdaitseu)laf(aIt-e3));GaillDNiA-tcri(S4,-suill4fa5tHe)e;xAil(D2-is-dulifSaEt,e)ai(l4I-,35)HGeaxlANaA(Ic-(34),G6-adlNisAuclf(a4t,e6)-; HPLC,high performanceliquid chromatography;ESI, electrospray ionization; MS, mass spectrometry; COSY, correlation spectroscopy; HOHAHA, homonuclear Hartmann-Hahn. Study of the binding domain to heparin cofactor II is the best known example showing the relationship between the structure and biological functions of dermatan sulfate [13]. The results of this previous study revealed a unique hexasaccharide structure containing a cluster of three IdoA(2-sulfate)-GalNAc(4-sulfate) repeats, which comprises only 5% of the disaccharides present in intact dermatan sulfate. We isolated and characterized the linkage region oligosaccharides from bovine aorta dermatan sulfate to examine possible structural variability and differences in this region from other glycosaminoglycans, especially chondroitin sulfate
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