Distribution and properties of amylase and lipase in alimentary tract of tilapia Oreochromis niloticus ×O.aureus

Three groups of tilapia (Oreochromis niloticus ×O.aureus), average body weight in groups Ⅰ,Ⅱ and Ⅲ as 55.14, 122.82 and 225.68 g respectively, were employed to study the development and distribution of digestive enzyme in alimentary tract. The results showed that the activities of amylase in total intestine rose sharply with the body weight increasing from 55 g to 122 g, and that went up slowly with increase of body weight from 122 g to 225 g. The activities of amylase and lipase in all groups showed the same regularity as those in fore intestine, which were higher than those in middle intestine. The activities of amylase and lipase hind intestine were the lowest. The relative ratio of amylase activity among fore, middle and hind intestines in the in three groups (Groups Ⅰ,Ⅱ and Ⅲ) were 10.950.52, 10.440.21 and 10.500.24, respectively;and the relative ratio of lipase activities among fore, middle and hind intestines in the three group (Groups Ⅰ,Ⅱ and Ⅲ) were 10.170.12,10.340.14 and 10.980.64. The relative ratio of amylase activities in the three group (Ⅰ,Ⅱ,Ⅲ) in hepatopancreas and total intestine were 13.439.31 and 18.2518.94 respectively;and the relative ratio of lipase activities in the three groups (Ⅰ,Ⅱ,Ⅲ) in total intestine were 13.8213.09. A group of tilapia (Oreochromis niloticus ×O.aureus) (average body weight as 111.81 g) were employed to study properties of digestive enzyme in alimentary tract. The results showed that the optimum pH for amylase in intestine and hepatopancreas were 6.5～7 and 7.5, respectively, and the optimum temperature for amylase in intestine and hepatopancreas was 30℃, and the optimum substrate concentration for amylase in intestine and hepatopancreas was 0.8%. The optimum pH and temperature for lipase were 7.0～7.5 and 35 ℃, respectively.