Comparison of tropomyosin released peptide and epitope mapping after in vitro digestion from fish (Larimichthys crocea), shrimp (Litopenaeus vannamei) and clam (Ruditapes philippinarum) through SWATH-MS based proteomics

Tropomyosin (TM) is a major shellfish allergen and a minor fish allergen. Different digestion profiles affect potential allergen anaphylaxis of protein. In this study, released peptides of fish-TM, shrimp-TM, and clam-TM by in vitro digestion of simulated gastric fluid (SGF), simulated intestinal fluid (SIF), and gastrointestinal (GI) were analyzed using sequential windowed acquisition of all theoretical fragment ion mass spectra (SWATH-MS) based proteomics. Results showed that digestion products of shrimp-TM yielded a lot of peptides matched T/B cell epitopes while core regions matched epitopes were distributed along the entire chain. Pepsin or trypsin-based digestion products of shrimp-TM presented many more peptides matched T/B cell epitopes compared with those of fish-TM and clam-TM. Besides, a differentiating peptide of VEKDKALSNAEGEVAAL (72-88) overlapped T/B cell epitopes could be used as a candidate peptide marker to identify tropomyosin allergen. These findings would supply new insight into the different allergenicity of tropomyosin.