Studies On The Digestive Enzymes Of Young Northern Sheatfish (Silurus Soldatovi)

Now the northern Sheatfish (Silurus soldatovi) culture becomes a new industry in oureconomy.In order to promote its culture in our country, it is very necessary to do some work on itsbasic research. In this study, the main digestive enzymes in northern Sheatfish were fully discussed.The physico-chemical characters (pH value, temperature and substrate-concentration)ofdigestive enzymes and the effect of feeding on the activity of protease,amylase and lipase in themain digestive organs of northern sheatfish were studied in this paper, simultaneity, the activities ofsome digestive enzymes and alkaline phosphatase were investigated during the larval and juveniledevelopment of northern sheatfish.The results are as follows.1. The optimum pH of protease in stomach is 2.6,protease in intestine canal is 9.8～10.3.Theoptimum pH of amylase in stomach is 6.0,amylase in intestine canal is 7.0～7.4.The optimumtemperature of protease in stomach is about 35℃, protease in intestine canal is 40～45℃, amylase instomach is 45℃, amylase in intestine canal is 40～45℃. The optimum substrate-concentration ofprotease in stomach and intestine canal are 0.5％casein,amylase in stomach is 0.5％dissolvablestarch.2. During the first developmental life of northern sheatfish (1～10 days old), the alkalineprotease, lipase and amylase activities changed very markledly,the acid protease activities appearedthe rising current gradually.The alkaline protease activities appeared the rising current in dailyfluctuating period. The result indicated that the larva of northern sheatfish had the effectiveactivities of the acid protease about 2 days old of hatching during the first developmental days.Thealkaline protease activities were better than the acid protease activities at the process of the entireforepart development, which achieved the high value in the 5 days old, subsequently, but the acidprotease achieved the high value in the 10 days old. The lipase change was steady in the process ofthe forepart development, the first high value appeared in the 4 days old. The amylase activity waseffective in the early phase,which decreased along the increase of days old.. The alkaline proteaseand amylase activities decreased in the 4th and 8th days old,but the lipase activities increased.At thedevelopment of northern sheatfish ,the digestive enzymes changed markedly in the alimentarytract,it showed that the digestive enginery was improving during the larval and juveniledevelopment of northern sheatfish.These patterns indicated a maturation of enterocytes and theacquisition of an adult mode of digestion within the first month of live.3. The activity of protease in stomach decreased after feeding,then increased and kept at a highlevel after 3h of feeding (P＜0.05). But the activity of protease in intestinal canal increased all alongand kept at a higher level after 4h of feeding.The effect of feeding on the activity of amylase indicated that the amylase in stomach decreased after 1h of feeding (P＜0.05), then increased andkept at a higher level after 3h of feeding, which was 15.87±2.02 U/mg protein.Trend of amylaseactivities in stomach change appeared from low to high.The activity of amylase in intestinal canalkept at a higher level after 5h of feeding. At the same time,the results showed the activity of lipasein stomach changed quite acutely, which kept at a higher level after 3h of feeding, but the activityof lipase in intestinal canal changed slack, The feeding effect the activity of lipase in stomach wasmore distinct than the activity of lipase in intestinal canal.