Neutral oligosaccharide structures linked to asparagines of porcine zona pellucida glycoproteins.

N-Linked sugar chains were liberated by hydrazinolysis from porcine zona pellucida glycoproteins obtained from ovarian follicular oocytes. Neutral sugar chains were separated from acidic ones by paper electrophoresis and fractionated with a serial lectin column chromatography and Bio-Gel P-4 column chromatography. Their structural analysis by sequential glycosidase digestion in combination with methylation analysis revealed that the neutral sugar chains are of bi-, tri-, and tetraantennary complex type with a fucosylated trimannosyl core. Twenty-six percent of the sugar chains contain N-acetyllactosamine repeating structures in their outer chain moieties. Only linear N-acetyllactosamine repeats, the maximum size of which is hexasaccharide, are detected. A characteristic feature is that 39% of the sugar chains contain N-acetylglucosamine residues at their nonreducing termini in spite of the absence of bisected sugar chains. This study provided, for the first time, the substantial information about the sugar chain structures of mammalian zona pellucida glycoproteins.