Abstract
BG60 is an important allergen of Bermuda grass (Cynodon dactylon) pollen, which causes allergic responses in human. It was suggested that its carbohydrate moiety may be relevant to allergic reaction (Su, S. N., Lau, G. X., Shu, P., Yang, S. Y., Huang, S. W., and Lee, Y. C. (1996) J. Allergy Clin. Immunol., in press). Therefore, the structure of the carbohydrate moiety in BG60 was investigated. The N-linked oligosaccharides were released from the glycopeptides of BG60 by digesting with a glycoamidase from sweet almond and reductively aminated with a fluorescent reagent, 2-aminopyridine. The mixture of pyridylaminated oligosaccharides were separated by high-performance liquid chromatography (HPLC) using an octadecylsilyl (ODS) column. Five oligosaccharide fractions were isolated, and each fraction was found to be homogeneous by HPLC on an amide-silica column. The structure of each of the oligosaccharides was analyzed by the two-dimensional mapping technique (Tomiya, N., Awaya, J., Kurono, M., Endo, S., Arata, Y., and Takahashi, N. (1988) Anal. Biochem. 171, 73-90), in tandem with sequential exoglycosidase digestion. The two most abundant oligosaccharides, A and B, have an unusual structural feature, i.e. the presence of an L-Fuc alpha-(1,3)-linked to Asn-linked GlcNAc without a Xyl beta-(1,2)-linked to the branching Man (see below). To the best of our knowledge, these are the first such oligosaccharides found in plant glycoproteins.
Highlights
BG60 is an important allergen of Bermuda grass (Cynodon dactylon) pollen, which causes allergic responses in human
We report the results of our structural investigation on the carbohydrate moiety of BG60 and found its major constituents are oligosaccharides hitherto unreported in the plant glycoproteins
The PA-oligosaccharides derived from BG60 were separated into five fractions by reverse phase high-performance liquid chromatography (HPLC) on the ODSsilica column (Fig. 1A)
Summary
BG60 is an important allergen of Bermuda grass (Cynodon dactylon) pollen, which causes allergic responses in human. Bermuda grass (Cynodon dactylon) pollen is one of the most common causes for airway allergic disease in hot and humid climate [1,2,3]. It contains at least 53 antigenic proteins that can induce immune response in rabbit [4], of which more than 12 have been shown to possess IgE binding activity (4 –7). We report the results of our structural investigation on the carbohydrate moiety of BG60 and found its major constituents are oligosaccharides hitherto unreported in the plant glycoproteins
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