Advancing allergen characterization in Perilla seed: an oil body purification approach

Perilla seed (PS), a common food in East Asia, has emerged as a leading cause of seed-induced anaphylaxis in Korean children, yet its allergenic proteins remain unidentified. Oleosins, hydrophobic oil-body (OB)-associated storage proteins, are recognized allergens in peanuts, hazelnuts, and sesame, and preliminary evidence suggests a similar role in PS. However, the intrinsic challenges of extracting lipophilic proteins have hindered systematic investigation. This study aimed to purify PS OBs, isolate oleosin under optimized conditions, and characterize candidate major allergens. Commercial Korean PSs were homogenized, and OBs were purified via sequential flotation. After defatting, proteins were separated by SDS-PAGE and tested by immunoglobulin E (IgE) immunoblotting using sera from pediatric PS-allergic patients. Protein bands corresponding to IgE binding were excised for LC-MS/MS analysis, and peptide spectra were searched against an in-house database using MASCOT. SDS-PAGE revealed multiple protein bands between 12 and 15, 20, 30-35, and ~ 50 kDa. IgE binding was observed at 12, 14-15, 20, 33, and 50 kDa, with inter-individual variability. LC-MS/MS consistently identified PS oleosin and oleosin-like proteins in the 12-15 kDa and 33 kDa regions, with the 14-15 kDa band showing the strongest identification (Mascot score up to 190). In conclusion, oleosin at 14-15 kDa, along with a probable 33 kDa dimeric form, represents the predominant allergenic protein in PS. This study provides the first systematic molecular characterization of PS oleosins and establishes a methodological framework for studying hydrophobic seed allergens.