ABSTRACT
The Japanese cedar pollen allergen (Cry j1) and the mountain cedar pollen allergen (Jun a1) are glycosylated with plant complex type N-glycans bearing Lewis a epitope(s) (Galß1-3[Fucα1-4]GlcNAc-). The biological significance of Lewis a type plant N-glycans and their effects on the human immune system remain to be elucidated. Since a substantial amount of such plant specific N-glycans are required to evaluate immunological activity, we have searched for good plant-glycan sources to characterize Lewis a epitope-containing plant N-glycans. In this study, we have found that three water plants, Elodea nuttallii, Egeria densa, and Ceratophyllum demersum, produce glycoproteins bearing Lewis a units. Structural analysis of the N-glycans revealed that almost all glycoproteins expressed in these three water plants predominantly carry plant complex type N-glycans including the Lewis a type, suggesting that these water plants are good sources for preparation of Lewis a type plant N-glycans in substantial amounts.
Subject(s)
Cryptomeria/chemistry , Epitopes/chemistry , Lewis Blood Group Antigens/chemistry , Polysaccharides/chemistry , Allergens/chemistry , Carbohydrate Sequence , Humans , Pollen/chemistry , Pollen/immunologyABSTRACT
We analyzed structural features of N-glycans linked to glycoproteins expressed in various seaweeds to identify new sources of biologically-important N-glycans or N-glycopeptides. Structural analysis of the N-glycans of glycopeptides prepared from pepsin digests of 15 species of seaweed revealed that only high-mannose type N-glycans occur in seaweed glycoproteins, and the Man9GlcNAc2 structure predominates in Sargassum fulvellum and Zostera marina, while no typical plant complex type N-glycans bearing ß1-2 xylosyl and α1-3 fucosyl residues present in either algae or seagrass. These results indicate that seaweeds lack the activities of several of the glycosyltransferases required for the biosynthesis of the complex type N-glycans found in terrestrial plants, and that the context of N-glycan processing in seaweeds is different from that in terrestrial plant cells.
Subject(s)
Glycoproteins/chemistry , Mannose , Polysaccharides/chemistry , Seaweed/chemistry , Gene Expression Regulation, Plant , Glycopeptides/chemistry , Glycopeptides/metabolism , Glycoproteins/metabolismABSTRACT
In developing plants, free N-glycans occur ubiquitously at micromolar concentrations. Such oligosaccharides have been proposed to be signaling molecules in plant development. As a part of a study to elucidate the physiological roles of de-N-glycosylation machinery involved in fruit ripening, we analyzed changes in the amounts and structural features of free N-glycans in tomato fruits at four ripening stages. The amount of high-mannose type free N-glycans increased significantly in accordance with fruit ripening, and the relative amounts of high-molecular size N-glycans, such as Man(8-9)GlcNAc(1), became predominant. These observations suggest that the de-N-glycosylation machinery, including endo-beta-N-acetylglucosaminidase (ENGase) activity, is stimulated in the later stages of fruit ripening. But contrary to expectation, we found that total ENGase activities in the tomato fruits did not vary significantly with the ripening process, suggesting that ENGase activity must be maintained at a certain level, and that the expression of alpha-mannosidase involved in the clearance of free N-glycans decreases during tomato fruit ripening.
Subject(s)
Fruit/growth & development , Fruit/metabolism , Glycoside Hydrolases/metabolism , Polysaccharides/chemistry , Polysaccharides/metabolism , Solanum lycopersicum/growth & development , Solanum lycopersicum/metabolism , Chromatography, Affinity , Concanavalin A/metabolism , Fruit/enzymology , Glycoproteins/metabolism , Solanum lycopersicum/enzymology , Mannose/chemistry , Mannose/metabolism , PigmentationABSTRACT
The pollen of oil palm (Elaeis guineensis Jacq.) is a strong allergen and causes severe pollinosis in Malaysia and Singapore. In the previous study (Biosci. Biotechnol. Biochem., 64, 820-827 (2002)), from the oil palm pollens, we purified an antigenic glycoprotein (Ela g Bd 31 K), which is recognized by IgE from palm pollinosis patients. In this report, we describe the structural analysis of sugar chains linked to palm pollen glycoproteins to confirm the ubiquitous occurrence of antigenic N-glycans in the allergenic pollen. N-Glycans liberated from the pollen glycoprotein mixture by hydrazinolysis were labeled with 2-aminopyridine followed by purification with 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, electrospray ionization mass spectrometry (ESI-MS), and tandem MS analysis, as well as exoglycosidase digestions. The antigenic N-glycan bearing alpha1-3 fucose and/or beta1-2 xylose residues accounts for 36.9% of total N-glycans: GlcNAc2Man3Xyl1Fuc1GlcNAc2 (24.6%), GlcNAc2Man3Xyl1GlcNAc2 (4.4%), Man3Xyl1Fuc1-GlcNAc2 (1.1%), GlcNAc1Man3Xyl1Fuc1GlcNAc2 (5.6%), and GlcNAc1Man3Xyl1GlcNAc2 (1.2%). The remaining 63.1% of the total N-glycans belong to the high-mannose type structure: Man9GlcNAc2 (5.8%), Man8GlcNAc2 (32.1%), Man7GlcNAc2 (19.9%), Man6GlcNAc2 (5.3%).
