Submitted to: Recent Progress in Medicinal Plants
Publication Type: Book / Chapter
Publication Acceptance Date: 8/30/2006
Publication Date: 2/25/2007
Citation: Chung, S., Kato, Y., Champagne, E.T. 2007. Reducing the allergenic properties of peanut allergens by copper/hydrogen peroxide. Recent Progress in Medicinal Plants. 15:443-453. Interpretive Summary: Peanut allergens are proteins that trigger allergic reactions in peanut-allergic individuals when ingested. One approach to reducing the allergenic potency of peanut allergens is to change their structures by linking them together. Copper ions (Cu2+) and hydrogen peroxide (H2O2) together, are known to link and convert proteins into big polymers. In this study, we determined if Cu2+ and H2O2 together can convert peanut allergens into big polymers, and if such reaction reduces the allergenic properties of peanut allergens. Extracts from raw and roasted peanuts were prepared, treated with Cu2+/H2O2, and analyzed for changes in allergenic potency using serum from peanut-allergic individuals. Results showed that levels of major peanut allergens were reduced, and big polymers were formed in roasted peanut extracts treated with Cu2+/H2O2. The treated extracts exhibited a lower allergenic property than the untreated. It was concluded that Cu2+/H2O2 reduced the allergenic potency of peanut extracts by reducing and converting major peanut allergens into polymers. This research may have a potential application in the development of hypoallergenic peanut-based products.
Technical Abstract: Copper ions (Cu2+) and hydrogen peroxide (H2O2) together are reported to catalyze the cross-linking of proteins through oxidation of their tyrosine residues. Such protein cross-links, which contain dityrosine, can also occur when proteins are treated with peroxidase (POD). Previously, we have shown that the allergenic properties of peanut allergens are reduced after treatment with POD. We hypothesized in this study that Cu2+/ H2O2 can also reduce peanut allergenicity, because Cu2+/ H2O2 produces the same cross-links (containing dityrosine) as POD. To support our hypothesis, extracts from raw and roasted peanuts were treated with Cu2+/ H2O2 at pH 7 for 5 hours at 37 oC, and analyzed by SDS-PAGE, Western blots, and competitive inhibition ELISA in which immunoglobulin E (IgE) antibodies from a pooled serum of peanut-allergic individuals were used. Also, a monoclonal antibody against dityrosine was used to detect dityrosine-containing cross-links. Results showed that only roasted peanuts were affected by Cu2+/ H2O2. In this case, levels of two peanut major allergens, Ara h 1 and Ara h 2, were reduced, and cross-links were formed. IgE binding, overall, was lower despite some binding of IgE to cross-links. Cross-links were recognized by the monoclonal antibodies against dityrosine. We concluded that Cu2+/ H2O2 reduced peanut allergenicity by catalyzing the decrease and cross-linking of peanut allergens.