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

如今，食物过敏正在成为一个严重的社会问题。人们对食物中的过敏原进行了积极的研究，发现了大量的过敏原。然而，作为胶乳-水果综合征，过敏原之间有一些相似之处。例如，植物过敏原中的糖基被认为具有共同的抗原性。我们观察到与Gly-m-Bd-28K和Tri-a-Bd-17K相似的现象。在本研究中，我们研究了Gly-m-Bd-28K和Tri-a-Bd-17K的糖基结构与其致敏性的关系。该产物与南瓜MP27/MP32和胡萝卜球蛋白样蛋白有很高的同源性。将产物的氨基酸序列与南瓜蛋白的氨基酸序列进行比较，表明该变应原是由南瓜蛋白的前蛋白形成的。过敏原与产品的前半部分相对应。此外，利用表达载体pGEX-6T在大肠杆菌中以谷胱甘肽S转移酶融合蛋白的形式表达了重组变应原，但重组变应原对Gly m Bd 28K敏感患者血清中的抗体反应较弱。从脱脂大豆片中提纯的变应原中的赖氨酰内肽酶得到的糖肽对IgE抗体有很强的反应，但糖肽中的脱糖肽不与IgE抗体反应。这些发现表明，变应原的糖部分与患者血清中的IgE抗体结合，并且糖部分是许多植物糖蛋白变应原的共同抗原决定簇。

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.