Trypsin-like Enzyme from Sand Crab (Portunus pelagicus): Purification and characterization

Studies with synthetic substrates and specific inhibitors indicated that a protcinase from the hepatopancreas of the sand crab (Portunus pelngicus) was a trypsin-like serine proteinase. The molecular weight of the enzyme estimated by gel filtration and mass spectrometry was ～ 25,000, whereas SDS-PAGE indicated a molecular weight of 34,800. The optimum temperature for hydrolysis of azocasein was 60°C, while inactivation of 50% enzymic activity occurred at 68°C. The enzyme, optimally active at pH 8.0 towards p-tosyl-L-arginine methyl ester and unstable at acid pH, was high in acidic amino acid residues. Under some conditions ihe knzyme readily autodigested. Our results can help understand and avoid problems of meat softening during storage of seafood products.