title: The poly(glycosyl) chains of glycoproteins. Characterisation of a novel type of glycoprotein saccharides from human erythrocyte membrane.
abstract: Glycopeptides with complex carbohydrate structure were isolated from delipidated human erythrocyte membranes after digestion with pronase. The poly(glycosyl)peptides isolated (apparent molecular weight 4000--13000) are suggested to contain 20--70 sugar residues in an alkali-stable saccharide chain linked through N-acetylglucosamine to asparagine. The main sugar components are galactose and N-acetylglucosamine, which together account for 80% of total sugars. That the compounds isolated are glycopeptides and not glycolipids is concluded from the following findings: only trace amounts of glucose and fatty acids were present, and no long-chain (sphingosine) bases could be detected; on the other hand, the amounts of mannose and amino acids found are compatible with an N-glycosidic poly(glycosyl)peptide structure. The structure of the poly(glycosyl)peptides was studied using methylation analysis, exoglycosidase treatments, acid hydrolysis of the native as well as the N-deacetylated glycopeptides, and chromium trioxide oxidation. The studies indicate that the poly(glycosyl)peptides contain a repeating-3)galactosyl(beta1-4)N-acetylglucosaminyl(beta1-structure with branch points at the C-6 of the galactose residues. The saccharide chains are terminated in N-acetylglucosaminyl, galactosyl, N-acetylneuraminyl(alpha2-3 and 6)galactosyl and fucosyl(alpha1-2)galactosyl residues, and they also contain blood group A and B determinants.
mesh_terms: D000596:Amino Acids / Q000032:analysis; D002241:Carbohydrates / Q000032:analysis; D004910:Erythrocyte Membrane / Q000378:metabolism*; D004912:Erythrocytes / Q000378:metabolism*; D006020:Glycopeptides / Q000032:analysis; D006023:Glycoproteins / Q000097:blood*; D006026:Glycoside Hydrolases; D006801:Humans; D008565:Membrane Proteins / Q000097:blood*; D008745:Methylation
chemical_list: D000596:Amino Acids; D002241:Carbohydrates; D006020:Glycopeptides; D006023:Glycoproteins; D008565:Membrane Proteins; D006026:Glycoside Hydrolases