Investigations on the oligosaccharide units of an A myeloma globulin

Abstract

The carbohydrate content of an A myeloma globulin was investigated. The carbohydrate content was found to be unchanged when the protein was isolated from the patient over a period of 18 months. The various polymeric forms of the protein contained similar proportions of carbohydrate. The A myeloma globulin contained approx. 2 residues of 6-deoxy-l-galactose (l-fucose), 14-15 of d-mannose, 12-13 of d-galactose, 12-13 of 2-acetamido-2-deoxy-d-glucose (N-acetyl-d-glucosamine), 6 of 2-acetamido-2-deoxy-d-galactose (N-acetyl-d-galactosamine) and 5 of N-acetylneuraminic acid (sialic acid), and these were distributed between six oligosaccharide units all of which were present on the heavy polypeptide chains. The oligosaccharide units showed two kinds of heterogeneity, which have been termed central and peripheral. Central heterogeneity was shown by the presence of three completely different core units, which had the following compositions: (1) 3 residues of d-galactose and 3 of 2-acetamido-2-deoxy-d-galactose, joined to protein by an O-glycosidic linkage between acetamidohexose and serine; (2) 3 residues of d-mannose, 2 of d-galactose and 3 of 2-acetamido-2-deoxy-d-glucose, joined to protein by an N-glycosidic linkage between acetamidohexose and aspartic acid; (3) 4 residues of d-mannose and 3 of 2-acetamido-2-deoxy-d-glucose with a linkage similar to that in (2). The core oligosaccharide units showed peripheral heterogeneity in the attachment of 6-deoxy-l-galactose, 2-acetamido-2-deoxy-d-glucose and N-acetylneuraminic acid. Tentative structures are proposed for these various types of oligosaccharide unit. Glycopeptides were isolated in which the sialic acid content exceeded that of d-galactose. Explanations are given for the electrophoretic mobility and staining characteristics of the various glycopeptides.

The Structure and Biology of Human IgD

“…One site was localized to the inter-Fd-Fc region and contained all the galactose and galactosamine, and the other two sites to the Fc fragment that contained only glucosamine (Figure 4). The carbohydrate moiety found in the inter-Fd-Fc region strikingly resembles that found in the homologous position in al chains (Dawson & Clamp 1968). It is heterogeneous with respect to sialic acid from molecule to molecule, which results in formation of multiple glycopeptide spots on peptide maps of d chains and multiple bands of the tryptic Fab fragments in starch gel analysis (Spiegelberg et al 1970b).…”

Amino acid sequence of the first 217 residues of a mouse heavy chain (MOPC 47A) with a domain deletion.

“…In order to simplify the analysis of the constant region of the 47A a chain, we would like to refer to the 47A a chain as a mouse al chain and to the 315 and 511 a chains as mouse tr2 chains by analogy to the human al and CV2 chains, the al chains in both species differing from the a2 chains in being covalently linked to their light chains and containing galactosamine in the hinge region (19,20).…”

A glycopeptide isolated from human gastric juice

“…It is probable that the peptide is a digestion product of a glycoprotein by pepsin, since the N-terminal residue was proline. The occurrence of two different types of carbohydratepeptide linkage in a protein has been observed in IgA and erythrocyte-membrane glycoproteins (Dawson & Clamp, 1968;Winzler, 1969;Hamazaki & Hotta, 1976). Glycopeptide 1 gave no precipitin reaction with anti-(human serum) and immunoglobulins and moreover showed H human-blood-group activity, suggesting that the peptide did not originate from immunoglobulins.…”