Identification and characterization of the allergens in the tomato fruit by immunoblotting

Background: Although the tomato fruit (Lycopersicon esculentum) has been widely investigated for breeding purposes, there have been few studies on tomato allergenicity. We attempted to identify the tomato fruit allergens and to compare the concentrations of IgE-binding proteins among the different growth stages with sodium dodecylsulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and immunoblotting. Methods: An immunoblot experiment on tomato fruit extracts was performed using sera from 11 patients with oral allergy syndrome (OAS) to tomatoes. Bands reacting with IgE from more than half of the OAS patients' sera were excised and subjected to determination of N-terminal amino acid sequences using the automated Edman degradation method. Moreover, we compared the concentrations of these proteins at each growth stage of the tomato fruit with SDS-PAGE and immunoblotting. Results: Four proteins binding with IgE from more than half of the OAS patients' sera were determined to be polygalacturonase 2A (PG2A), β-fructofuranosidase, superoxide dismutase (SOD) and pectinesterase (PE). The concentrations of PG2A, β-fructofuranosidase and PE were highest in the red ripening stage with both SDS-PAGE and immunoblotting. Conclusion: The concentrations of 3 of 4 tomato allergens increased during ripening.