The major peanut allergen,Ara h 2, functions as a trypsin inhibitor,and roasting enhances this function

BACKGROUND: The widespread use of peanut products, the severity of the symptoms, and its persistence in afflicted individuals has made peanut allergy a major health concern in western countries such as the United States, United Kingdom, and Canada. In a previous study, the authors showed that the allergenic properties of peanut proteins are enhanced as a result of thermal processing. OBJECTIVE: The purpose of this investigation was to determine whether any specific functions are associated with the major peanut allergen, Ara h 2, and whether the functionality of this protein is influenced by processing. An assay was developed and used to assess structure/function changes in Ara h 2 induced by roasting and the effect of these alterations on the allergenic properties of this major peanut allergen. METHODS: A protein domain homology search was used to determine possible functions for Ara h 2. One of the putative functions (protease inhibition) was tested by means of appropriate enzyme assays and protein gel electrophoresis. Circular dichroism was used to compare the structural properties of Ara h 2 purified from raw and roasted peanuts. RESULTS: Ara h 2 purified from peanuts is homologous to and functions as a trypsin inhibitor. Roasting caused a 3.6-fold increase in trypsin inhibitory activity. Functional and structural comparison of the Ara h 2 purified from roasted peanuts to native and reduced Ara h 2 from raw peanuts revealed that the roasted Ara h 2 mimics the behavior of native Ara h 2 in a partially reduced form. CONCLUSIONS: The data indicate that thermal processing might play an important role in enhancing the allergenic properties of peanuts. Not only has it previously been shown to affect the structural and allergic properties of peanut proteins but also, for the first time, the functional characteristics of an allergen. These structural and functional alterations are likely to influence the allergenicity of peanuts.