In vitro characterisation of tropomyosin from flower tail shrimp, Metapenaeus dobsoni and effect of hydrolysis on allergenicity of tropomyosin

Shellfish allergy due to major allergen tropomyosin can lead to anaphylaxis in highly sensitive individuals. Tropomyosin purified from flower tail shrimp, Metapenaeus dobsoni was subjected to in vitro characterisation. Also effect of trypsin and chymotrypsin hydrolysis on shrimp allergenicity was evaluated. The purified tropomyosin was profiled by SDS PAGE and de nova sequenced using MALDI TOF. Peptide sequence showed a significant protein score in the range of 72-137 with 95% confidence level. In silico mapping of IgE-binding regions showed conservation of IgE-binding regions along with cross reactivity with other species. The most abundant amino acid present was glutamic acid followed by lysine. IgE-binding ability got significantly (P < 0.05) reduced by hydrolysis in comparison to raw. The lower peptide fragments resulted from chymotrypsin hydrolysis by SDS PAGE were very feeble than by trypsin and no immunological activity was observed. Chymotrypsin hydrolysis is observed to be effective in retarding immunological activity of tropomyosin both at 37 degrees C and 50 degrees C compared with trypsin hydrolysis at 37 degrees C by immunoblotting analysis. This can be further utilised in the processing of crustacean extracts intended for seasoning purpose. Further research on in vivo assays for reduced immunoreactivity of tropomyosin after hydrolysis of shrimp can be carried out. Practical applications In vitro characterisation of tropomyosin helps in understanding the cross reactivity with other shrimp species. Chymotrypsin hydrolysed shrimp can be utilised in the processing of crustacean extracts intended for seasoning purpose.