Blood group substances glycoproteins

Figure 52-6. Diagrammatic representation of the structures of the H, A,and B blood group substances. R represents a long complex oligosaccharide chain, joined either to ceramide where the substances are glycosphingolipids, or to the polypeptide backbone of a protein via a serine or threonine residue where the substances are glycoproteins. Note that the blood group substances are biantenna ry ie, they have two arms, formed at a branch point (not indicated) between the GIcNAc—R, and only one arm of the branch is shown. Thus, the H, A,and B substances each contain two of their respective short oligosaccharide chains shown above. The AB substance contains one type A chain and one type B chain.

Figure 9.12 Deoxy derivatives. These contain one less oxygen atom than the monosaccharide from which they are derived. 2-Deoxyribose is a most important deoxy pentose and is a major constituent of deoxyribonucleic acid (DNA). Deoxy hexoses are widely distributed among plants, animals and microorganisms especially as components of complex polysaccharides. Examples are rhamnose (6-deoxymannose), a component of bacterial cell walls, and fucose (6-deoxygalactose), which is often found in glycoproteins and is an important constituent of human blood group substances.

Glycoproteins are proteins that have been modified by the addition of one or more carbohydrate groups. Glycoproteins include blood group substances, among many others. 

The animal and plant worlds have yielded some of the more fascinating carbohydrate-based polymers as homo- and heteropolysaccharides, as glycoproteins, as lipopolysac-charides, and as glycolipids, to mention a few. Blood group substances, antigenic determi-... 

There are other lysosomal disorders in addition to those shown in Figure 9.20 and Table 9.1. For instance, several types of fucosidoses exist, which affect such structures as glycoproteins and blood group substances. Sialidoses also exist. However, lysosomal fucosidase and sialidase (neuraminidase) deficiencies do not affect the degradation of gangliosides. 

The reaction of partially purified, lima-bean lectin with hog gastric-mucin type A substance exemplified the precipitin-like curve obtained for lectin-polysaccharide or -glycoprotein reactions.103 Classical precipitin-curves between purified components II and III and type A blood-group substance were also obtained.151,199 Maximal precipitation of component II (equivalence) occurred at a lower ratio of A substance per mole of protein than for component III. Under conditions where type A substance precipitated 90% of the lectin, types A2 and B precipitated151,199 66 and 13%, respectively, of component II, and 21 and 0% of component III. Neither of the lima-bean lectins precipitated with type O blood-group substance. 

The composition of neutral glycoproteins and blood group substances... 

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