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Identification and characterization of IgE -binding proteins in soybean lecithin

Xuelin Gu, University of Nebraska - Lincoln

Abstract

Soybean lecithin is widely used as an emulsifier in processed food products, pharmaceuticals, and cosmetics. It is also used as a health supplement. However, the health concern has been raised that soybean lecithin may carry soybean allergens. The allergenicity of soybean lecithin proteins has been thoroughly assessed in this study.^ Two-dimensional electrophoresis and image analysis showed that six soybean lecithin samples have very similar protein profiles. These soybean lecithins contain common major proteins. However, there are significant differences in the amount of most constituent proteins.^ The results of immunoblotting with IgE from soy sensitive individuals showed that soy lecithin contained a relatively high proportion of potential allergens. These potential allergens include four 39 kDa components (pI 4.40, 4.60, 4.95, and 5.20), a 20-kD component (pI 4.40), and four 12 kDa components (pI 4.38, 4.70, 5.00, and 5.30).^ The results of Edman N-terminal amino acid sequence and/or MS analysis revealed that the four 39 kDa components are the isoforms of a same soy protein. The function of this protein is unknown. The component of 20 kDa (pI 4.40) is soybean Kunitz trypsin inhibitor (SKTI). This is the Tia isoform of SKTI according to its pI as determined by two-dimensional electrophoresis. SKTI is a known soybean allergen. The component of 12 kDa/pI 4.38 is large subunit of soybean albumin. This methionine rich soybean protein and a soybean allergen was newly identified in this study. The amino acid sequences of three peptide fragments from the soy lecithin protein with MW of 7 kDa and pI of 9.85 matched 100% with a known allergen originating from Blomia tropicalis mite. ^ Large subunit of soybean albumin, the 7 kDa protein (pI 9.85), and four 39 kDa allergens are major proteins in all soy lecithin samples used in this study. The soy lecithin allergens showed relatively high stability to pepsin digestion in simulated gastric fluid. Therefore, soy lecithin is a potential allergenic source. ^

Subject Area

Biology, Molecular|Agriculture, Food Science and Technology|Health Sciences, Immunology

Recommended Citation

Gu, Xuelin, "Identification and characterization of IgE -binding proteins in soybean lecithin" (2001). ETD collection for University of Nebraska - Lincoln. AAI3009719.
http://digitalcommons.unl.edu/dissertations/AAI3009719

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