Structures of N-Linked Oligosaccharides of Glycoproteins from Tobacco BY2 Suspension Cultured Cells

Abstract

  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 (Man₃Fuc₁Xyl₁GlcNAc₂ (41.0%), GlcNAc₂Man₃Fuc₁Xyl₁GlcNAc₂ (26.5%), GlcNAc₁Man₃Fuc₁Xyl₁GlcNAc₂ (21.7%), Man₃Xyl₁GlcNAc₂ (3.3%)), and the minor class was a high-mannose type (Man₅GlcNAc₂ (7.5%)). This is the first report to show that α(1→3) fucosylation of N-glycans does occur but β(1→4) galactosylation of the sugar chains does not in the tobacco cultured cells.