Peanut (Arachis hypogaea L.) is grown extensively worldwide for its edible seed and oil. Proteomics has become a poweful tool in plant research; however, studies involving legumes, and especially peanuts, are in their infancy. Furthermore, protein expression in the peanut seed coat (skin), which is a distinct plant structure that is critical for seed development and defense, has never been explored. Accordingly, a comparative proteomic study of peanut seed and skins was performed. A phenol-based extraction procedure was necessary to exract skin proteins, as this material is naturally high in tannins that readily bind and precipitate proteins. Extractions were followed by filter-aided sample preparation, nanoLC-MS/MS sequencing, and Arachis hypogaea database searching. Peanut skins contained many known peanut allergens (Ara h 1-11) in addition to 38 proteins not identified in the seed including several defense proteins with antifungal activity. Western blotting using sera of peanut allergic patients revealed that peanut skin proteins bound peanut-specific IgE when isolated from phenolic compounds, but not when phenolic compounds were present. These findings have important implications for the potential allergenicity and food uses of peanut skins (processing byproduct) and provide a first step towards understanding their specialized function. Related, research is ongoing to identify proteins in the seed and seed coat that are differentially expressed in response to drought, as this information will aid efforts at developing drought/aflatoxin resistant cultivars. Additionally, proteomics can be used to understand roasting induced protein modifications, information with important implications for allergenicity. To this end, proteins from raw and variably roasted peanuts were compared. Roasted samples contained several proteins with modified lysine residues (carboxyethyllysine, carboxymethyllysine, and pyralline), indicative of Maillard browning. This research demonstrates the utility of proteomics to evaluate protein expression and modifications in peanuts and peanut skins with important agronomic and food science applications.

Proteomic analysis of differential protein expression and processing induced modifications in peanuts and peanut skins

246th National Meeting (2013)

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