Structural characterization of the N-linked carbohydrate chains from mouse zona pellucida glycoproteins ZP2 and ZP3

N-linked oligosaccharides of mouse zona pellucida glycoproteins ZP2 and ZP3 were prepared as pyridylaminated derivatives. Anion-exchange HPLC revealed that 95% or more of them are acidic. About 80% of these acidic chains were neutralized by digestion with Arthrobacter ureafaciens sialidase and a small amount of sulfate was found in the residual acidic chains. The neutralized fractions (SN fractions) from ZP2 and ZP3 were similarly fractionated by size-fractionation HPLC into many peaks having different numbers of LacNAc in the non-reducing regions. The SN fractions from ZP2 were cleaved by endo-beta-galactosidase into the core and non-reducing regions. The tri- and tetra-antennary complex-type chains with a Fuc residue were predominant in the core region. On the other hand, four kinds of fragment containing the LacNAc sequence were obtained from the non-reducing region. Sialic acids were shown to be linked to the core fragments, as well as the non-reducing fragments. The N-linked oligosaccharides of ZP3 were suggested to have essentially the same structures as those of ZP2.