STUDY ON THE RELATIONSHIP BETWEEN THE STRUCTURE OF THE SUGAR MOIETIES OF PLANT ALLERGENS AND THEIR ALLERGENICITIES

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Nowaday, food allergy is becoming a great social problem. Allergens in food have been actively elucidated and a great number of the allergens have been found. However, as the latex-fruit syndrome, some similarity among allergens have been pointed out. As an example, the sugar moieties in plant allergens are proposed to show a common antigenicity. We observed similar phenomena cas to Gly m Bd 28K and Tri a Bd 17K.In the present study, we examined the relationship between the structure of the sugar moieties of Gly m Bd 28K and Tri a Bd 17K and their allergenicities.A cDNA encoding Gly m Bd 28K has been cloned. The product for cDNA has been shown to exhibit high homology with pumpkin MP27/MP32 and a carrot globulin-like protein. In comparison of the amino acid sequence of the product with that of the pumpkin protein, the allergen was indicated to be formed via a preproprotein from its proprotein. The allergen corresponded to the former half part of the product. Furthermore, a recombinant allergen was expressed as a fusion protein with glutathione S-transferase in Eschericia coli using an expression vector pGEX-6T.However, the recombinant allergen showed weak response against IgE antibodies in the sera of Gly m Bd 28K-sensitive patients. The glycopeptide obtained with lysyl endopeptidase from the allergen which was purified from defatted soybean flakes, showed strong response to the IgE antibodies, but the deglycosylated peptide from the glycopeptide did not react with the IgE antibodies. These findings suggest that the sugar moiety of the allergen binds to IgE antibodies in the sera of the patients, and that the sugar moiety acts as a common antigenic determinant in many plant glycoproteinic allergens.