Blood-group polysaccharides structure

Bourne, E. J. See also. Barker, S. A. Bouveng, H. O., and Lindberg, B., Methods in Structural Polysaccharide Chemistry, 15, 53-89 Brady, Robert F., Jr., Cyclic Acetals of Ketoses, 26, 197-278 Bray, H. G., D-Clucuronic Acid in Metabolism, 8, 251-275 Bray, H. G., and Stacey, M., Blood Group Polysaccharides, 4, 37-55 Brimacombe, j. S. See How, M. J. Butter worth, Roger F and Hanes-siAN, Stephen, Tables of the Properties of Deoxy Sugars and Their Simple Derivatives, 26, 279-296... 

Relatively few zoopolysaccharides have been isolated in pure condition, and few have had a fairly complete structural analysis. Glycogen, chitin, hyaluronic acid, heparin, chondroitin sulfates, and the blood-group polysaccharides are the best known and defined. The early work in this field has been summarized by P. A. Levene (1), who is also responsible for much of the nomenclature. Among the early workers were 0. Schmiedeberg, F. Miil-ler, 0. Hammersten, C. Neuberg, P. A. Levene, and associates. 

Figure 14.2 Representative oligosaccharide structures found on mammalian glycoproteins and glycolipids. The complex oligosaccharides may be bi-, tri-, or tetra-antennary the branches may be more or less elongated with 1—>4 linked lactosamine units, and they may or may not be sialylated. The SLex, Lea, and Leb structures represent the different blood group determinants often present on lipids, and the elongated core 2 structure is a mucin-type glycosylation. Proteoglycans have a common core to which a variety of linear acidic polysaccharides are attached.

Fortunately from the chemists point of view, there are polysaccharides with blood group activity more readily accessible than those from erythrocytes, and it is with the former that most chemical investigations have been concerned, although the relationship between these and the blood group substances proper from erythrocytes is not yet clear. Indeed the relationship may be no more than a close similarity in chemical structure of some parts of the molecular complex. 

While it is impossible to make any precise statement regarding the structure of this blood group A polysaccharide until our present investigations are more advanced, it does seem possible that the structure of the alkali-stable carbohydrate residue is of a ramified type, bearing some general relationship to that deduced for ovomucoid, which, however, is much less resistant to hydrolysis than is this blood group A polysaccharide. 

Often, a polysaccharide gives a polymeric residue after a Smith degradation. Methylation analyses of this material and of the original polysaccharide may nonetheless furnish valuable structural information. It is also possible to subject the material to successive Smith degradations, a notable example being the stepwise degradation of the ovarian-cyst, blood-group H substance (42) by Lloyd and Kabat.100... 

Structurally, the O-polysaccharide chains of H. pylori clinical isolates have a poly-A-acetyl-lactosamine (-LacNAc) chain decorated with multiple lateral a-L-fucose residues forming internal Lex determinants with terminal Lex or Ley units (Fig. 10.4) or, in some strains with additional, D-glucose or D-galactose residues (Moran 2001 a,b, 2008 Monteiro, 2001). Moreover, Lea, Leb, sialyl-Lex, and H-1 antigens have been structurally described in other strains, as well as the related blood groups A and B (Fig. 10.4), but occur in association with Lex and LacNAc chains (Monteiro et al., 2000a,b Heneghan et al., 2000). 

The agglutination of incompatible red blood cells, which indicates that the body s immune system has recognized the presence of foreign cells in the body and has formed antibodies against them, results from the presence of polysaccharide markers on the surface of the cells. Types A, B, and 0 red blood cells each have characteristic markers, called antigenic determinants, type AB cells have both type A and type B markers. The structures of all three blood-group determinants are shown in Figure 25.15. 

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