Carbohydrate-peptide linkages glycoproteins, structures

Table V. Structures of Carbohydrate-peptide Linkages in Glycoproteins...

In this Section, the nature of the linkages between the protein chain and the carbohydrate moieties in glycoproteins will be considered, and some indication of their occurrence will be given. It will become clear that, in a number of examples, a given polypeptide chain is glycosidically substituted at more than one point. Sometimes, the amino acid residue at two such points is of a different type, so that more than one type of carbohydrate-peptide bond occurs in the same protein, It is likely that more examples of this kind of structure will be found as more features of the constitution of glycoproteins involved in membranes and connective tissue are determined. 

Properties and Structure. a -Acid glycoprotein (a -AGP) has a molecular mass of about 41,000 and consists of a peptide chain having 181 amino acid residues and five carbohydrate units (14,15). Two cystine disulfide cross-linkages connect residues 5 and 147 and residues 72 and 164. The carbohydrate units comprise 45% of the molecule and contain siaUc acid, hexosamine, and neutral hexoses. In phosphate buffer the isoelectric point of the... 

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