Всероссийский научно-исследовательский институт физиологии, биохимии и питания животных – филиал Федерального государственного бюджетного научного учреждения «Федеральный научный центр животноводства – ВИЖ имени академика Л.К. Эрнста»
ABSTRACT. Тhe aim of the study was to investigate the temperature characteristics of peptidases hydrolyzing the protein components of food in sabrefish Pelecus cultratus (L.), family of Cyprinidae). Fish are caught in the Volga ridge of the Rybinsk Reservoir. Morphometric analysis of the body was carried out, the intestine was removed, placed on an ice bath, intestinal fat was removed, it was cut along and the contents were removed with tweezers and the bowel was not washed. The intestinal mucosa from 4 fish was mixed, homogenates were prepared using a cooled Ringer's solution for cold-blooded animals at pH 7.4. Homogenates and substrate were incubated in the temperature range of 0-70 ° C for 30 min. Casein was used as a substrate to determine the activity of trypsin-like peptidases (AT), hemoglobin was used to determine activity of chymotrypsin-like peptidases (ACh), pH 7.4. The activity of peptidases of the intestinal mucosa was determined by the increment of tyrosine per 1 minute of incubation, taking into account the background in terms of 1 g of tissue. The value of AT of the intestinal mucosa at a temperature of 20°C is 8.12 ± 0.20, that of ACh is 1.92 ± 0.14 μmol/(g·min). The curves of the temperature dependence of AT and ACh of the intestinal mucosa are similar and do not correspond to the classical bell-shaped form; in the range of 10-60°C, the level of relative activity of peptidases is close to the value of the temperature optimum (60°C). At the temperature of active feeding of fish, the Q10 values for AT and ACh of the intestinal mucosa are close to 1, for ACh in the zone 0-10°C it is 1.1. The Eact value for AT in the low temperature zone (0-10°C) is 1.06 kcal/mol, in the zone of higher temperatures (10-60°C) - 0.09, for ACh - 1.77 and 0.52 kcal/mol, respectively. The lower values of Eact, in comparison with the data of other researchers, can be due to the fact that the digestion of the protein components of the food in sabrefish in a wide range of temperatures requires less energy. On the other hand, since in the present work, in the preparation of homogenates, all the enzymes that function in the area of the brush border of the enterocytes were retained, the higher total proteolysis rate probably was due to the effects of interaction of individual enzymes in the peptidase system. Such effect of positive cooperativity in digestive processes can play an important role in fish and other poikilothermic animals.
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