| Abstract: | Four trypsin‐like enzymes (CP‐I, II, III and IV in order of elution on DEAE‐Sepharose chromatography), purified from the hepatopancreas of crawfish, were inhibited by protease inhibitors such as phenyl methyl suifonyl fluoride (PMSF), soybean trypsin inhibitor (SBTI), aprotinin and tosyl lysine chloromethyl ketone (TICK). The molecular weights of CP‐I, II, III and IV were determined to be 35.0, 41.2, 37.9 and 39.5 kDa, respectively, using sodium dodecyl sulfate polyacryl‐amide gel electrophoresis (SDS‐PAGE), These proteases had optimal esterase activity at pH 8.0–8.5 and showed the highest activity at 60–70C. Crawfish proteases were rich in acidic amino acids. Activation energies for hydrolysis of tosyl arginine methyl ester (TAME) by these proteases were 6.98 – 8.34 kcal/mole. Unlike other serine proteases, the activities of CP‐I and CP‐II were activated by mercury while CP‐HI and IV were inhibited. |
