The relationship of the structure of peanut proteins to their function as allergens.

Authors: Maleki, Soheila; YAMAKI, KOHJI - NFRI; Schmitt, David; Champagne, Elaine; SHINOHARA, KAZUKI - NFRI

Submitted to: United States Japan Natural Resources Protein Panel
Publication Type: Proceedings
Publication Acceptance Date: 10/1/2002
Publication Date: 12/1/2002
Citation: Maleki, S.J., Yamaki, K., Schmitt, D.A., Champagne, E.T., Shinohara, K. 2002. The relationship of the structure of peanut proteins to their function as allergens. United States Japan Natural Resources Protein Panel. HHH-1:HHH-6.

Interpretive Summary: The significant, growing and costly portion of the Food and Drug Administration (FDA) food recalls have been due to mislabeled products that contain allergens. Meanwhile, little is known about the reason why certain foods are allergenic. A few classic characteristics have been associated with allergenicity. Some of these characteristics are resistance to heat, acid and digestive enzymes, as well as having enzymatic or enzymatic inhibitory activity. Generally, it is thought that the more stable a protein is, the more likely that it can be detected by the immune system and cause a reaction, but there are few explanations for increased stability of allergens. In this study we have shown that one of the major allergens is a digestive enzyme inhibitor and that roasting enhances this activity. This is the first study to show an increase in allergenicity of an allergen due to enhanced function caused by roasting. If we can understand why roasting enhances the allergenic properties of peanuts, we can devise a method to reduce the allergenicity of peanuts.

Technical Abstract: The significant, growing and costly portion of the FDA s food recalls have been due to mislabeled products that contain allergens. Meanwhile, little is known about the reason why certain foods are allergenic. Even less is known about what happens to the allergenicity of food products after processing. In order to assess the consequences of processing on the allergenic properties of peanut proteins, the biophysical and immunological differences between roasted and raw peanut proteins were examined. In assessing the purified, individual allergens from raw and roasted peanuts, we determined that the sequence of one of the major peanut allergens, Ara h 2 is homologous to trypsin inhibitors. An enzymatic assay was used to show that Ara h 2 functions as a trypsin inhibitor and most significantly, Ara h 2, purified from roasted peanuts (roasted Ara h 2) was found to be several fold more active as a trypsin inhibitor than the Ara h 2 purified from raw peanuts (raw Ara h 2). In order to assess the effect of these alterations in peanut proteins in vivo, mouse sensitization experiments were performed. We found that mice were more likely to be sensitized when treated with roasted peanuts than with raw peanuts. Our findings suggested that the structural and functional changes due to food processing contribute to increased allergenic properties of peanut proteins and may indeed enhance the possibility of becoming sensitized to peanuts.