Digestive enzyme activities in crab Charybdis japonica

The effects of temperature and pH on the activities of protease,amylase,cellulase and lipase in the midgut gland and the distribution of the digestive enzymes in different parts of the digestive organs of crab Charybdis japonica were studied by the enzymatic analytical method.The optimal temperatures were found at 55 ℃ for protease,35 ℃ for amylase,65 ℃ for cellulase and 45 ℃ for lipase.The optimal pH values were observed at 6.2 for protease,5.5 for amylase,4.4 for cellulase,and 7.5 for lipase.Under the optimum conditions,the protease,cellulase and lipase had higher activity in the midgut gland than that in the stomach and intestine,the midgut gland being the most important organ for secretion of the digestive enzymes.The activity of protease in different digestive organs was in the descentant order arranged as midgut glandstomachintestine,the activities of cellulase and lipase as midgut glandintestinestomach.Amylase had the similar activitv as that in the midgut gland,stomach and intestine.