Extraction and mass spectrometry identification of a major peach allergen Pru p 1

Peach allergy can be caused by the allergen Pru p 1. This occurs by cross-reactivity with the homologous birch pollen allergen Bet v 1. However, the direct identification of Pru p 1 as an immunoglobulin E (IgE)-binding protein extracted from peach fruit has never been reported.Phosphate-buffered saline (PBS) and phenol extractions were applied to solubilise the proteins from peach peel and pulp, and IgE immunoblotting with sera of individual peach-allergic patients was used to detect the potential allergens. Most of the patients showed binding to an 18 kDa band in IgE immunoblotting performed with the phenolic extracts of peach peel and pulp, but not when the PBS extracts were used. Mass spectrometry of the 18 kDa spot excised from a two-dimensional electrophoretic gel showed this protein to correspond to the peach allergen Pru p 1.Phenol extraction was necessary to detect by IgE immunoblotting a major peach allergen, which showed very low extractability with PBS, indicating the appropriateness of adopting different extraction procedures to identify plant allergens. The 18 kDa peach protein was definitively identified as the Bet v 1-homologous peach allergen Pru p 1.