The isolation and characterization of major allergens from walnut (Juglans regia) and peanut (Arachis hypogaea)

Major allergens from walnut (Juglans regia) and peanut (Arachis hypogaea) have been purified and characterized. Jug r 1, a 2S protein and major allergen from walnut, consists of a large and small subunit joined by disulfide bonds. Post-translational processing of Jug r 1 is similar to that of other 2S proteins. Jug r 1 is IgE reactive in both the reduced and non-reduced state as determined by immunoblott analysis. Ara h 2 and Ara h 6 2S proteins from peanut are major allergens. Ara h 2 and Ara h 6 are monomeric 2S proteins that do not undergo the post-translational processing seen with most 2S proteins. Carbohydrate was not detected with any of the 2S proteins isolated from either walnut or peanut. Cross reactivity studies between the 2S proteins from walnut and peanut indicate that patients hypersensitive to both foods have allergies mediated by two separate two separate IgE pools. Ara h 2, Ara h 6, and Jug r 1 were all found to be extremely resistant to pepsin digestion utilizing a simulated gastric system. Upon reduction with dithiothreitol the proteins were easily digested by pepsin. Pancreatin in simulated intestinal fluid was able to digest Ara h 2, Ara h 6, and Jug r 1 in the non-reduced state. Two other allergens were also isolated from walnut. These proteins migrated at 34 and 45 kDa when developed with SDS-PAGE. The 34 and 45 kDa proteins contain the highest degree of homology with the highly conserved basic subunit of legumin proteins. Further characterization of food allergens is necessary if we are to generate an understanding of the basic mechanisms which dictate the allergenic properties of these proteins. Our findings have added to the growing fist of allergenic 2S proteins. The indigestible nature of the 2S proteins and other major food allergens has also been demonstrated. Continued work on the digestibility of allergens may lead to the development of foods that are more digestible and therefore less allergenic.