A novel method using immuno-affinity chromatography for isolating β-conglycinin from soybean proteins

Effects of heat treatment on the antigenicity, antigen epitopes, and structural properties of β-conglycinin

In this study, the effects of heat treatment on antigenicity, antigen epitopes, and structural changes in β-conglycinin were investigated. Results showed that the IgG (Immunoglobulin G) binding capacity of heated protein was inhibited with increased temperature, although IgE (Immunoglobulin E) binding capacity increased. Linear antigen epitopes generally remained intact during heat treatment. After heat treatment, β-conglycinin was more easily hydrolyzed by digestive enzymes, and a large number of linear epitopes was destroyed. In addition, heat denaturation of β-conglycinin led to the formation of protein aggregates and reduction of disulfide bonds. The contents of random coils and β-sheet of heated β-conglycinin decreased, but the contents of β-turn and α-helix increased. Moreover, the protein structure of heated β-conglycinin unfolded, more hydrophobic regions were exposed, and the tertiary structure of β-conglycinin was destroyed. Heat treatment affected the antigenicity and potential sensitization of β-conglycinin by changing its structure.

Development of immunoaffinity chromatographic method for isolating glycinin (11S) from soybean proteins

A monoclonal antibody (Mab), 4B2, against soybean glycinin was prepared using the preliminary extracted natural glycinin as the immunogen in our previous study. Herein, we established a novel method for the purification of glycinin by Mab 4B2-based immunoaffinity chromatography. The characteristics of the purified glycinin were identified by SDS-PAGE, Western blot, and histamine release assay. Glycinin was successfully isolated from soybeans with a yield of 16.8% and a purity of 93.8%, which were significantly higher than those produced using other traditional procedures. The acidic polypeptides of the purified glycinin can be recognized by the Mab 4B2, but not the basic polypeptides. In addition, the histamine release ratio of the purified glycinin was similar to that of natural glycinin, which indicated that the purified glycinin maintained its biological activities. Further study revealed that the Mab/gel ratios ranging from 6.0 to 12.0 mg/mL were suitable for the isolation of glycinin using immunoaffinity chromatography. Taken together, this new method based on immunoaffinity chromatography could be used for high-yield and high-purity natural glycinin production and would facilitate future study on the mechanism of soybean-induced food allergy.

Saikosaponin-d inhibits β-conglycinin induced activation of rat basophilic leukemia-2H3 cells

β-Conglycinin is one of the major storage proteins in soybean and has been identified as a potential diagnostic marker for severe allergic reactions to soybean. Unfortunately, there is a lack of information on the signal transduction pathways of β-conglycinin induced mast cell activation and how to alleviate these allergic reactions. Bupleurum falcatum, a traditional oriental medicine, has been widely utilized in the treatment of influenza, fever, malaria and menstrual disorders. Furthermore, it has been reported that saikosaponins, the important principle of B. falcatum, possesses anti-allergic activities. Therefore, the present study investigated whether or not saikosaponin-d, an extract of B. falcatum, was effective in the treatment of allergic reactions cased by β-conglycinin, using a rat basophilic leukemia-2H3 cell line. There were multiple signaling pathways contributing to the development of β-conglycinin-mediated rat basophilic leukemia-2H3 cell activation. The intracellular calcium mobilization and tyrosine phosphorylation were early events, which in turn elicited reactive oxygen species production, gene activation of Cdc42 and c-Fos, and ultimately led to β-hexosaminidase release. Saikosaponin-d inhibited rat basophilic leukemia-2H3 cell degranulation by suppressing these critical incidents in the signal transduction pathway. These results suggest that saikosaponin-d exhibited anti-allergic activity and could become an effective herbal therapy for alleviating soybean allergy.