Effect of Phenol on the Activity and Temperature Characteristics of Peptidases in Chironomid Larvae at Different pH Values

The effect of phenol (Ph, 0.25 mmol/L) on the activity and temperature dependence of casein- and hemoglobin-lytic peptidases functioning in the whole organism of chironomid larvae Chironomus sp. within the temperature range of 0-70 degrees C at different pH values (3.0, 5.0, and 7.4) is studied. The temperature optimum of the studied peptidases of chironomid larvae corresponds to 40 degrees C. Under the influence of phenol, the activity of casein-lytic peptidases increases more significantly at 20 degrees C and pH 5.0 (by a factor of 3.3) and that of hemoglobin-lytic peptidases increases more significantly at pH 3.0 (by a factor of 3.5). The effect successively decreases from pH 3.0 up to pH 7.4. under both temperatures. In the presence of phenol, the shape of the curves of the temperature dependence and the Q(10) values transform most significantly in the zone of high temperatures. The values of activation energy (E-act) of the process of hydrolysis of casein and hemoglobin-lytic peptidases in the zone of low and high temperatures are different. In the presence of phenol, E-act values of the process of hydrolysis of casein casein-lytic peptidases at pH 7.4 increase; at pH 5.0 they decreases in the zone of high temperatures. The values of E-act of the process of hydrolysis of hemoglobin-lytic peptidases decrease in most cases. The mechanisms of the influence of phenol on peptidase activity and digestive processes in benthivorous fish feeding on chironomid larvae are discussed.