Activity and temperature characteristics of digestive tract enzymes in sterlet <i> Acipenser ruthenus</i> (L.)
The activity of proteinases and glycosidases of digestive tract in sterlet Acipenser ruthenus (L.), grown in aquaculture conditions as well as temperature characteristics of proteinases were investigated. In hungry fish pepsin-like activity was 6.6-8.5 folds lower than those in feeding fish. The activity of trypsin-like proteinases was approximately order of magnitude higher than glycosidase activity. The character of the proximal-distal gradient of enzyme activity in sterlet is close to that of ichthyophages from natural waters. The values of the temperature optimum of pepsin-like proteinase of stomach mucosa correspond to 40ºC, trypsin-like proteases of the intestine - 50ºC, chymotrypsin-like proteases - 60ºC. In the temperature range for fish feeding, trypsin-like proteinases of chyme have higher values of their relative activity (35-80%) compared to those of the mucosa (5-50%). At this temperature range, E <sub>act</sub> <sub></sub>value of stomach mucosa is 2.5 kcal/mol. E <sub>act</sub> <sub></sub>value of intestinal mucosa and chyme does vary depending on temperature. But in the zone of 0-20ºC they are significantly lower than in the zone of higher temperature.