Polyphenol oxidase/caffeic acid may reduce the allergenic properties of peanut allergens

Abstract

Abstract Polyphenol 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 the allergenic properties by cross‐linking the allergens. Because caffeic acid, a phenolic compound, can cross‐link proteins, its effect on peanut allergens was also examined. In the experiments, peanut extracts were treated with and without PPO, PPO/caffeic (pH 8, 37 °C for 1 h) 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 the levels 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 IgE binding or 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. Copyright © 2005 Society of Chemical Industry