N-Linked Oligosaccharides of Glycoproteins from Ginkgo biloba Pollen, An Allergenic Pollen

Abstract

The pollen of Ginkgo biloba is one of the allergens that cause pollen allergy symptoms. The plant complex type N-glycans bearing β1-2 xylose and/or α1-3 fucose residue(s) linked to glycoallergens have been considered to be critical epitopes in various immune reactions. In this report, the structures of N-glycans of total glycoproteins prepared from Ginkgo biloba pollens were analyzed to confirm whether such plant complex type N-glycans occur in the pollen glycoproteins. The glycoproteins were extracted by SDS-Tris buffer. N-Glycans liberated from the pollen glycoprotein mixture by hydrazinolysis were labeled with 2-aminopyridine and the resulting pyridylaminated (PA-)N-glycans were purified by a combination of size-fractionation HPLC and reversed-phase HPLC. The structures of the PA-sugar chains were analyzed by a combination of two-dimensional sugar chain mapping, IS-MS, and MS/MS. The plant complex type structures (GlcNAc₂Man₃Xyl₁Fuc₁GlcNAc₂ (31%), GlcNAc₂Man₃Xyl₁GlcNAc₂ (5%), Man₃Xyl₁Fuc₁GlcNAc₂ (13%), GlcNAc₁Man₃ Xyl₁Fuc₁ GlcNAc₂ (8%), and GlcNAC₁Man₃Xyl₁GlcNAc₂ (17%)) have been found among the N-glycans of the glycoproteins of Ginkgo biloba pollen, which might be candidates for the epitopes involved in Ginkgo pollen allergy. The remaining 26% of the total pollen N-glycans have the typical high-mannose type structures: Man₈GlcNAc₂ (11%) and Man₆GlcNAc₂ (15%).

• plant glycoprotein
• antigenic N-glycan
• sugar chains
• pollen allergy
• Ginkgo biloba