Isolation and Characterization of Poly(glycosyl)ceramides (Megaloglycolipids) with A, H and I Blood‐Group Activities

Abstract

Very complex glycosphingolipids with A, H and I blood-group activities were isolated from human erythrocyte membranes. The membranes were obtained from erythrocytes of blood group A, A2 a n d 0 respectively. A general formula for the antigens is:(where Fuc is fucose, Gal is galactose, GlcNAc is N-acetylglucosamine and Glc is glucose) with values of y2 ranging from 10-27. A-active preparations contain additionally 2-3 residues of N-acetylgalactosamine. In view of the unusual complexity of these compounds they were designated poly(glycosy1)ceramides (formerly megaloglycolipids). Individual poly(glycosy1)ceramide fractions were isolated from A erythrocytes and were found to differ by about 8 glycosyl residues per molecule forming a series of compounds with 22, 30, 38, 51 and 59 glycosyl residues per mole. Structural studies indicate that the main sequence of poly(glycosy1)ceramides consists of the residues of galactopyranose and 2-deoxy-2-acetamidoglucopyranose substituted at 3 and 4 position respectively. These residues are probably alternating. N-Acetylglucosamine substituted at 3 position was not found in poly-(glycosy1)ceramides. Branches of poly(glycosy1)ceramides originate from 3 and 6 position of galactopyranosyl residues. The number of branches is proportional to the degree of molecular complexity. In poly(glycosy1)ceramides isolated from A and A2 erythrocytes the branches are terminated with the following structures GalNAc CI 1 +3 [Fuc CI 1 '21 Gal; Fuc CI 1 -i2 Gal and Gal (presumably Gal 1 -+4 GlcNAc). In poly(glycosy1)ceramides from A cells the total number of A and H-active structures per average molecule of 30-35 glycosyl residues amounts to 2.1 and 1.2 respectively while the number of terminal galactose structures is 1.8. For poly(glycosy1)ceramides from A2 erythrocytes the corresponding figures are 0.75, 3.5, and 2.1 respectively.Poly(glycosy1)ceramides from 0 cells comprise about 3.8 H-active structures and 1.8 terminal galactopyranosyl residues. In poly(glycosy1)ceramides with high "n" values the number of terminal galactose structures is increased. These fractions display high blood-group I activity. However, the removal of terminal galactose with P-galactosidase affects I-activity only slightly.

Blood-group-Ii-active gangliosides of human erythrocyte membranes

“…Other studies have indicated that blood-group-I activities are also carried on gangliosides (Yokoyama & Plocinik, 1965) and glycolipids (Anstee & Tanner, 1975). A glycolipid with ten carbohydrate units (Watanabe et al, 1975) and others with 22-60 carbohydrate residues (polyglycosylceramides or macroglycolipids) (Gardas, 1976;Koscielak et al, 1976) has been shown to carry blood-group-I in addition to blood-group-ABH activities. An anti-(blood-group i)-like cold agglutinin, from patient McC, has been reported to react with lacto-N-neotetraose or the glycosphingolipid termed paragloboside, both of which have the same carbohydrate structure, Galfil -4GIcNAcflI-> 3Gal,61-*4Glc (Tsai et al, 1976).…”

Alkali‐stable blood group A‐ and B‐active poly(glycosyl)‐peptides from human erythrocyte membrane

“…0.02 M phosphate buffer (pH 7.5) and 10 vol. butan-l-01 to solubilize the poly(glycosyl)ceramides [3]. The insoluble residue was further delipidated by homogenization in chloroform-methanol (2: 1 and 1:2, v/v).…”

“…It has been reported that blood group ABH activity is present also in glycoproteins of the erythrocyte membrane [4-91. However, since these observations have been mainly based on serological inhibition tests, the presence of blood group-active glycolipids in the glycoprotein preparations cannot be excluded. Owing to the water solubility of the large-molecular size blood groupactive glycosphingolipids (the poly(glycosyl)ceramides), it has been suggested that these glycosphingolipids may have been regarded in some studies as glycoproteins [3]. The occurrence of protein-bound blood group ABH antigens in the erythrocyte membrane has therefore still been a matter of some controversy.…”

Structural similarity of the terminal carbohydrate sequences of glycoproteins and glycolipids

“…The occurrence of a new type of heteroglycans containing saccharide chains of 20-60 sugar residues was recently demonstrated for glycolipids [71,72] and glycoproteins [73] of human erythrocyte membrane. This type of chains account for a major fraction of the carbohydrates of glycolipids [74] and glycoproteins [75-771 of the erythrocyte membrane.…”

“…In glycolipids the carbohydrate is joined to the ceramide via a lactose unit [71,72]. The glycopeptrdes from the erythrocyte membrane do not contain glucose, but they contain mannose, and have an alkalistable linkage to asparagine [73,76].…”