Submitted to: Journal of the Science of Food and Agriculture
Publication Type: Peer reviewed journal
Publication Acceptance Date: 2/15/2005
Publication Date: 7/18/2005
Citation: Chung, S., Champagne, E.T., Kato, Y. 2005. Polyphenol oxidase/caffeic acid may reduce the allergenicity of peanut allergens. Journal of the Science of Food and Agriculture. 85:1631-2637. Interpretive Summary: Peanut allergens are proteins and culprits that make people allergic to peanuts. Reducing their allergenic properties will be beneficial to peanut-allergic individuals. In this study, we attempted to reduce peanut allergenicity by using polyphenol oxidase (POD). POD is an enzyme that causes browning in fruits (e.g., apples) and vegetables (e.g., lettuce) when they are cut or damaged. In the experiment, we treated peanut allergen extracts with POD. POD then transformed portions of the allergens into big polymers. As a result, the polymers became less allergenic. Further investigation indicates that peanut allergenicity was further reduced when caffeic acid, a compound in fruits and vegetables, was added. The finding suggests that POD together with caffeic acid may have a potential application in the development of hypoallergenic peanut-based products. Peanut allergic individuals, pregnant women, and young children will particularly benefit from these hypoallergenic products. Ultimately, sale and consumption of peanut products are expected to increase, and the peanut industries will continue to grow.
Technical Abstract: Phenol oxidase (PPO) catalyzes the oxidation of tyrosine residues of proteins, and therefore, their cross-linking. Previously, we demonstrated that cross-links produced by peroxidase (POD), which also catalyzes tyrosine oxidation, led to a reduction in the allergenic properties of peanut allergens. We postulated in this study that PPO can also reduce peanut allergenicity by cross-linking the allergens. Because caffeic acid, a phenolic compound, can cross-link proteins, its effect on peanut allergenicity was also examined. In the experiments, extracts from raw and roasted peanuts were treated with and without PPO, PPO/caffeic (pH 8, 37 oC for 1 hr) and caffeic acid (pH 10.5, overnight), respectively. The samples were then analyzed for cross-links and IgE binding by SDS-PAGE, western blots, and competitive inhibition ELISA. Results showed that in all cases, cross-links and a decrease of two peanut major allergens, Ara h 1 and Ara h 2, were observed. Of the three treatments, PPO/caffeic was the most effective in reducing the allergenic properties of peanut allergens. The availability of tyrosine residues was also demonstrated in a POD-treated system, using a monoclonal antibody against dityrosine. We concluded that PPO/caffeic acid reduced the allergenic properties of Ara h 1 and Ara h 2 by cross-linking and decreasing the levels of allergens.