Quantitative Analysis of Oligosaccharide Structure of Glycoproteins

Abstract

A sensitive and quantitative method for the structural analysis of oligosaccharide was established for the glycoform analysis of glycoproteins. In this study, N-linked oligosaccharides of human IgG and bovine transferrin were analyzed for the evaluation of the method. Carbohydrate moiety of glycoprotein was released by hydrazinolysis and purified by paper chromatography. The oligosaccharides were labeled with a fluorescent dye, 2-amino-benzamide, for the enhancement of detection sensitivity. Sialylated (acidic) oligosaccharides were separated from neutral oligosaccharide by employing a strong anion-exchange column (MonoQ) followed by the treatment with sialidase. Enzymatically desialyated fractions and neutral fractions of oligosaccharides were applied to normal-phase HPLC to resolve the peaks according to glucose unit (GU). The structure of separated molecules was further determined by sequential digestion with exoglycosidases. As a result, disialylated biantennary complex-type oligosaccharide was found to be a major sugar chain in bovine transferrin (63%). In human IgG, core fucosylated asialobiantennary complex oligosaccharides were dominant. These results coincided well with reported results.