Characterization of endogenous proteases from lizardfish (Saurida Wanieso) viscera and associated salt-dependent properties.
To effectively utilize the lizardfish viscera generated as a by-product of surimi manufacturing, the properties of endogenous proteases in the viscera were investigated. Two protease activity groups were identified from lizardfish viscera, and their optimal temperature and pH were 55oC and 7.0, and 45oC and 11.0, respectively. The results of protease inhibitory and fluorogenic substrate specificity assays showed that both dominant proteases belong to the serine protease family. Also, the effects of NaCl on the catalytic activity and thermal stability of proteases from viscera were clarified. The catalytic activity of protease would increase after incubation in NaCl solutions (5-25%) for 30 days and the thermal stability of proteases was also enhanced markedly in 15% NaCl solution. All the results demonstrated the salt-dependent behavior of proteases in NaCl solution and that NaCl-dependent changes in catalytic activity and thermal stability have potential applications for the production of fermented food.