The temperature dependence of casein- and hemoglobinlytic peptidases functioning in the whole organism of chironomid larvae Chironomus plumosus, food objects of adult benthophages and juvenile fish of various ecological groups, was studied within the temperature range of 0–70 ºС at different рН values (3.0, 5.0 and 7.4). The method of mixed samples was used to determine the activity and characteristics of enzymes. Homogenates of previously crushed and carefully mixed dozens of larvae were used as enzymatically active preparations. Activity of peptidases was assayed by the increase in tyrosine concentration using the Folin-Ciocalteu reagent. It is shown that the activity of peptidases that function in the tissues of chironomid larvae depends to a considerable extent on temperature and рН, but the pH has a smaller effect on the activity and the temperature dependence of casein- and hemoglobin-lytic peptidases than temperature. The temperature optimum of the studied peptidases of chironomid larvae corresponds to 40 ºС. The Q10 values in the zone of vital temperatures are slightly changed. They are, as a rule, increased in the zone of 30–40 ºС, and are sharply decreased in the zone of high temperatures. The values of activation energy of the process of hydrolysis of casein and hemoglobin in the zone of low and high temperatures are different. The Еact values of the process of hydrolysis of casein and hemoglobin at a temperature not exceeding 20 ºС are usually below those in the zone of higher temperatures (except for hemoglobin-lytic peptidases at pH 5.0). The data obtained indicate a significant effect of pH not only on the activity, but also on the temperature characteristics of peptidases that function in the body of chironomid larvae. Differences in the characteristics of casein- and hemoglobin-lytic peptidases in chironomid larvae at different temperatures and pH can influence the digestion in benthophages and fry of all fish species.

The effects of crystalline and amorphous phenol (0.5 mmol/L) on the characteristics of glycosidases, as well as casein-lytic and hemoglobin-lytic peptidases, which function in the whole body of chironomid larvae Chironomus sp. were studied. Crystalline phenol decreased the activity of glycosidases in comparison to the control in the temperature range 0–50 ºС, amorphous phenol – in the temperature range 0–70 ºС. The temperature optimum of glycosidases in whole body of chironomid larvae in control and experiment corresponds to 50 ºС. The activity of glycosidases in comparison to the control decreased in the pH range 5–11 (to a greater extent in the case of the lower fraction). Amorphous phenol increased the activity of casein-lytic peptidases in comparison to the control in the temperature range of 30–50 ºС, hemoglobin-lytic peptidases – in the temperature range of 0–60 ºС. The degree of the increase of enzyme activity in the temperature optimum zone of casein-lytic and hemoglobin-lytic peptidases was different: the level of enzyme activity in the experiment was higher than in the control by 2.3 and 1.8 times, respectively. The temperature optimum of the studied peptidases of chironomid larvae, regardless of the experimental conditions, corresponds to 40 °C. Crystalline phenol did not actually affect the Q10 values of glycosidases in the temperature range 0–50 °C. Amorphous phenol decreased the Q10 values at a temperature of 40–50 °C. The Q10 values of casein-lytic peptidases increased in most cases, the Q10 values of hemoglobin-lytic peptidases decreased in the presence of amorphous phenol. The process of protein hydrolysis was characterized by a break in the Arrhenius plot at 20 °C. The values of Еact in the range 0–20 °С were lower than in the zone of higher temperatures. The Еact values of the process of casein hydrolysis by peptidases of all tissues of chironomid larvae in the presence of amorphous phenol in both temperature zones increased. The Еact values of the process of hemoglobin hydrolysis by peptidases of all tissues of chironomid larvae in the presence of amorphous phenol in both temperature zones decreased. The Еact values of the process of starch hydrolysis in the presence of crystalline phenol decreased. The amorphous phenol changed the Еact values in different directions. They slightly increased in the presence of the phenol upper fraction, but they decreased in the presence of the phenol lower fraction. The data obtained indicate a significant effect of crystalline and amorphous phenol not only on activity, but also on the characteristics of peptidases and glycosidases that function in the whole body of chironomid larvae.

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