Co-Authors:
Birk, Y., Hebrew University, Faculty of Agriculture, Rehovot, Israel
Harpaz, I., Hebrew University, Faculty of Agriculture, Rehovot, Israel
Ishaaya, I., Hebrew University, Faculty of Agriculture, Rehovot, Israel
Bondi, A., Hebrew University, Faculty of Agriculture, Rehovot, Israel
Abstract:
The optimal conditions for total proteolytic activity in vitro of the midgut as well as whole-larva homogenates of Tenebrio molitor L. were determined as pH 6·2-6·4, 37°C for 20 min reaction, and 0·5% casein. The same were found for both Tribolium confusum Duval and T. castaneum Herbst except for the pH, which was in the range of 6·5-6·9. Larvae of Tribolium grown under a fluctuating temperature, with a mean of 24·5°C, showed a remarkably increased proteolytic activity, as compared to those grown under a constant temperature of 28°C. The crystalline soybean trypsin inhibitor partially inhibited proteolysis in Tenebrio larvae, whereas the C1 fraction of soybeans inhibited some 70 per cent of this activity. Haemoglobin could not replace casein as a substrate. Moreover, when added to reaction mixtures containing optimal casein concentrations it inhibited proteolysis to a considerable extent. Likewise, larval growth of all three species was suppressed on basic diets supplemented with haemoglobin. The addition of methionine and/or isoleucine to the haemoglobin-supplemented diets could not overcome this suppression of growth. With a relative decrease in proteolytic activity during larval development there is a steady relative increase in amylolytic activity until both activities reach constant levels in the last instars. © 1962.
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