Characterization by nuclear magnetic resonance of the concanavalin A binding oligosaccharide on the βb chain of placental β-hexosaminidase B: lectin binding to the separated polypeptide chains of hexosaminidases A and B

The type and distribution of the oligosaccharides on each polypeptide of human placental β-hexosaminidases A (α(βaβb)) and B (2((βaβb)) were examined. The denatured polypeptides were separated by isoelectric focussing in a polyacrylamide slab gel and each gel was then overlaid with 125I-labelled lectins. The study indicated that the βa chain contains negligible carbohydrate, the βb chain contains both the high-mannose and a complex type oligosaccharide, and the α chain contains predominantly high-mannose or hybrid type moieties. Two asparagine-linked high-mannose type oligosaccharides present on the βb polypeptide of β-hexosaminidase B were isolated by concanavalin A chromatography and by reverse-phase high pressure liquid chromatography. Proton nuclear magnetic resonance characterization of the oligosaccharides revealed an equimolar glycan mixture of the high-mannose type structure Man5 and Man6.