All Three Subunits of Soybean -Conglycinin Are Potential Food Allergens

Soybeans are recognized as one of the “big 8” food allergens. IgE antibodies from soybean-sensitive patients recognize more than 15 soybean proteins. Among these proteins only the R-subunit of -conglycinin, but not the highly homologous R′and -subunits, has been shown to be a major allergenic protein. The objective of this study was to examine if the R′and -subunits of -conglycinin can also serve as potential allergens. Immunoblot analysis using sera collected from soybean-allergic patients revealed the presence of IgE antibodies that recognized several soy proteins including 72, 70, 52, 34, and 21 kDa proteins. Matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF) analysis of trypsin-digested 72, 70, and 52 kDa proteins indicated that these proteins were the R′-, R-, and -subunits of -conglycinin, respectively. Additionally, purified R′-, R-, and -subunits of -conglycinin were recognized by IgE antibodies present in the soybeanallergic patients. The IgE reactivity to the -subunit of -conglycinin was not abolished when this glycoprotein was either deglycosylated using glycosidases or expressed as a recombinant protein in Escherichia coli. The results suggest that in addition to the previously recognized R-subunit of -conglycinin, the R′and -subunits of -conglycinin also are potential food allergens.