ACTIVITY DISTRIBUTION OF DIGESTIVE PROTEASES FROM NEMIPTERUS VIRGATUS AND THEIR RESPONSES TO pH VALUE AND TEMPERATURE

摘要

In the present study, three groups (Ⅰ-Ⅲ) of Nemipterus virgatus, with average body weights of 154.36, 250.72 and 329.09 g, respectively, were used to investigate the changes in the activity and distribution of digestive proteases in different organs and sections of the digestive tract. Another group of N. virgatus (average body weight of 188.41 g) was used to analyze the changes in the activity of digestive proteases in response to various pH values and temperatures. The activity of digestive proteases in all analyzed organs increased with the increase of body weight at the range of 154.36-329.09 g. The activities of digestive proteases in the different sections of the digestive tract were compared, and a similar change was found among groups Ⅰ-Ⅲ. The activities of digestive proteases from various organs were in a descending order: pylorus ceca > stomach > foregut > midgut > hindgut > hepatopancreas. Through observing the zymograms of substrate-sodium dodecil sulphate-polyacrylamide gel electrophoresis, many kinds of digestive proteases could be found in different organs and the varieties were changed with the change of body weight. Two peaks in the diagram between protease activity and pH value were found at pH 3.0 and 10.0, respectively. The activity under alkaline condition was 60% higher than that under acidic condition. The optimal temperature for protease activity was 50C, while the protease activity at 10C was only 30% of that at 50C.