Structures of N-linked oligosaccharides of glycoproteins from tobacco BY2 suspension cultured cells

The structures of N-linked sugar chains of glycoproteins expressed in tobacco BY2 cultured cells are reported. Five pyridylaminated (PA-) N-linked sugar chains were derived and purified from hydrazinolysates of the glycoproteins by reversed-phase HPLC and size-fractionation HPLC. The structures of the PA-sugar chains purified were identified by two-dimensional PA-sugar chain mapping, ion-spray MS/MS analysis, and exoglycosidase digestions. The five structures fell into two categories; the major class (92.5% as molar ratio) was a xylose containing-type (Man(3)Fuc(1) Xyl(1)GlcNAc(2) (41.0%), GlcNAc(2)Man(3)Fuc(1)Xyl(1)GIcNAc(2) (26.5%), GlcNAc(1)Man(3)Fuc(1)Xyl(1)GIcNAc(2) (21.7%), Man(3) Xyl(1)GlcNAc(2) (3.3%)), and the minor class was a high-mannose type (Man(5)GlcNAc(2) (7.5%)). This is the first report to show that (alpha(1-->3) fucosylation of N-glycans does occur but beta(1 --> 4) galactosylation of the sugar chains does not in the tobacco cultured cells.