TRYPSIN-LIKE-ENZYME FROM SAND CRAB (PORTUNUS-PELAGICUS) - PURIFICATION AND CHARACTERIZATION

Studies with synthetic substrates and specific inhibitors indicated th at a proteinase from the hepatopancreas of the sand crab (Portunus pel agicus) was a trypsin-like serine proteinase. The molecular weight of the enzyme estimated by gel filtration and mass spectrometry was almos t-equal-to 25,000, whereas SDS-PAGE indicated a molecular weight of 34 ,800. The optimum temperature for hydrolysis of azocasein was 60-degre es-C, while inactivation of 50% enzymic activity occurred at 68-degree s-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 r esidues. Under some conditions the enzyme readily autodigested. Our re sults can help understand and avoid problems of meat softening during storage of seafood products.