Tropomyosin allergen from freshwater and marine water crabs: Identification, structural-physicochemical, rheological and allergenic characterization

The aim of the present investigation was to purify and characterize highly allergenic tropomyosin from economically important crab species of freshwater and marine sources. Among the six crab species, the highest level of tropomyosin was detected in the raw samples of Scylla olivacea (5.68 ± 0.2 mg/g), whereas the lowest level was detected in the raw samples of Charybdis ferriatus (3.13 ± 0.2 mg/g). The electrophoretic analysis of purified tropomyosin showed the presence of bands within the range of 32–38 kDa. The purified tropomyosin obtained from S. olivacea (freshwater) and C. ferriatus (marine provenience) was found to have lower allergenicity threshold levels of 238.93 ppb and 225.58 ppb as revealed by enzyme-linked immunosorbent assays (ELISA). The tropomyosin with more allergenicity was further characterized for its structural, physico-biochemical, and thermal properties using Fourier transform infrared (FT-IR) spectroscopy, high-performance liquid chromatography (HPLC), and thermogravimetric analysis (TGA). FTIR revealed the presence of arginine in the allergen tropomyosin which plays an important role in eliciting allergenicity. TGA confirmed better stability in the crab allergen tropomyosin compared to that of standard tropomyosin. The flow behavior studies of allergenic tropomyosin revealed less viscous and shear-thickening behavior.