The structures of the asparagine-linked sugar chains of human apolipoprotein B-100

Abstract

The asparagine-linked sugar chains of human apolipoprotein B-100 were liberated from the polypeptide portion by hydrazinolysis followed by N-acetylation and NaB 3H 4 reduction. Their structures were elucidated by sequential exoglycosidase digestion in combination with methylation analysis after fractionation by paper electrophoresis and gel permeation chromatography. One neutral and two acidic fractions were obtained by paper electrophoresis in a molar ratio of 7:8:5. The neutral fraction contained high-mannose type oligosaccharides consisting of Man 5GlcNAc 2 to Man 9GlcNAc 2. The acidic fractions contained monosialylated and disialylated biantennary complex type oligosaccharides. As minor components in the monosialylated fraction, biantennary complextype oligosaccharides which were absent one terminal galactose residue, monoantennary complex type, and hybrid type oligosaccharides were detected. Apolipoprotein B-100 was calculated to contain 5–6 mol of high-mannose type and 8–10 mol of complex type oligosaccharides per mole protein.