Disaccharides, sulfated

ASs are able to hydrolyze a variety of sulfate esters. Depending on the enzyme specificity the physiological substrates include, among others, small mono- and disaccharide sulfates, hydrophobic steroids, and amphiphilic sulfated carbohydrates found in glycosaminoglycans (GAGs). However, small synthetic aryl sulfates are the... 

A disaccharide is added to a pyridine SO3 complex solution, which is prepared by reacting 5 to 6 times the molar amount of liquid SO3 as much as that of disaccharide with 5 to 10 times the amount of pyridine as that of the disaccharide at 0°C to 5°C, for sulfation at 50°C to 70°C for 3 to 7 hours. After the completion of sulfation, the greater part of pyridine Is removed by decantation. The obtained solution exhibits an acidity that is so strong that it is improper to apply the reaction with aluminum ion and, therefore, sodium hydroxide is added for neutralization. After the remaining pyridine is removed by concentration, 100 unit volumes of water per unit volume of the residue is added thereto. To the solution is then added aluminum ion solution mainly containing aluminum dihydroxychloride, the pH of which is 1.0 to 1.2, in such an amount that the aluminum ion Is present in an amount of 4 to 6 molar parts of the amount of disaccharide to provide a pH of 4 to 4.5. The mixture is reacted under stirring at room temperature and the formed disaccharide poly sulfate-aluminum compound is allowed to precipitate. After filtration, the residue is washed with water and dried. 

Proteoglycans linked to chondroitin sulfate by the Xyl-Ser O-glycosidic bond are prominent components of cartilage (see below). The repeating disaccharide is similar to that found in hyaluronic acid, containing... 

GlcUA but with GalNAc replacing GlcNAc. The GalNAc is substituted with sulfate at either its 4 or its 6 position, with approximately one sulfate being present per disaccharide unit. 

As shown in Figure 48-8, the keratan sulfates consist of repeating Gal-GlcNAc disaccharide units containing sulfate attached to the 6 position of GlcNAc or occasionally of Gal. Type 1 is abundant in cornea, and type II is found along with chondroitin sulfate attached to hyaluronic acid in loose connective tissue. Types I and II have different attachments to protein (Figure 48—8). 

The repeating disaccharide contains glucosamine (GlcN) and either of the two uronic acids (Figure 48-9). Most of the amino groups of the GlcN residues are N-sulfated, but a few are acetylated. The GlcN also carries a Cg sulfate ester. 

Figure 48-9. Structure of heparin. The polymer section illustrates structural features typical of heparin however, the sequence of variously substituted repeating disaccharide units has been arbitrarily selected. In addition, non-O-sulfated or 3-0-sulfated glucosamine residues may also occur. (Modified, redrawn, and reproduced, with permission, from Lindahl U et al Structure and biosynthesis of heparin-like polysaccharides. Fed Proc 1977 36 19.)...

Carvalho, R. S. H., Tersariol, I. L. S., Nader, H., and Nakaie, C. R., First purification of heparan sulfate disaccharides with an amine resin used as solid support for peptide synthesis, Anal. Chim. Acta, 403, 205, 2000. 

D-Clucuronic acid residues in heparin are linked as in disaccharide units 1 and 2, that is, either to 2-acetamido-2-deoxy-D-glucose ( Ana) or to 2-deoxy-2-sulfoamino (ANS) residues. (Although not apparent from Scheme 1, the amino sugar can be sulfated at C-6.)... 

Whereas a major proportion of the 2-acetamido-2-deoxy-D-glucosyl residues is probably nonsulfated at C-6 (C-sulfation is expected to require prior N-sulfation),23 various degrees of C-sulfation have been reported for N-acetylated regions of heparan sulfates,148,149 and a 6-C-sul-fated, N-acetylated disaccharide was isolated from heparanase digests of heparan sulfates.114,115... 

From pig mucosa. Notations as for Scheme 1. Major products (yield 40-80% of original heparin). Major disaccharide fraction (50-80%). From heparin chains terminating with a D-glucuronic acid residue at the reducing end. Minor products (yield <3% of original heparin). From the active site for antithrombin (asterisk denotes 3-C-sulfation of the amino sugar or anhydro-D-mannose). 

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