Identification of two alkaline proteases and a trypsin inhibitor from muscle of white croaker (Micropogon opercularis)

Extracts from white croaker skeletal muscle showed two alkaline proteases and a trypsin inhibitor when they were chromatographed in DEAE‐Sephacel. The activity against azocasein was maximal at pH 8.5 and 9.1 for proteases I and II, respectively. Both enzymes showed optimum activity at 60° C. The molecular masses were found to be 132 kDa for protease 1,363 kDa for protease II, and 65 kDa for the inhibitor. Protease I showed the characteristics of a trypsin‐like enzyme, and protease II those of a SH‐enzyme. These proteins may play important roles in mechanisms of cellular proteolysis.