Effects of temperature and pH on the protease and amylase activities in skewband grunt Hapalogenys nitens

The effects of temperature and pH on protease and amylase activities in skewband grunt Hapalogenys nitens was studied. Results showed that the pH values of the stomach, hepatopancreas and intestine were 4.9-5.4, 5.8-6.2, and 6.5-6.9 respectively. Protease activity rose with the increase of water temperature with a peak at 40 C, and then decreased. The order of protease activity was as follows: stomach>foregut>pyloric caecum>hindgut>hepatopancreas. The optimum temperature for amylase in H. nitens was 35 C within the range of 15 -50 C, the order of amylase activity was as follows: hepatopancreas>pylorie caecum>foregut>hindgut>stomach. The optimum pH for protease activity in stomach was 2.8 C within the range of 2.2--7.6, while the optimum pH for protease activity in other digestive organs was 7.2 C with in the range of 4.8-8.0. Under the optimum pH conditions, the order of protease activity in different organs was as follows: foregut>pyloric caecum>hindgut>hepatopancreas. The optimum pH for protease activity in