Co-Authors:
Ishaaya, I., The Volcani Center, Agricultural Research Organization, Bet Dagan, Israel
Ascher, K.R.S., The Volcani Center, Agricultural Research Organization, Bet Dagan, Israel
Shuval, G., The Volcani Center, Agricultural Research Organization, Bet Dagan, Israel
Abstract:
The effect of the antifeeding compound AC-24,055 on the main digestive enzymes of Spodoptera littoralis was determined. The inhibitory effect of AC-24,055 on the amylolytic and proteolytic activity increased with concentration and was well correlated with the antifeedant activity. After 3-day feeding on sugar beet leaves treated with 0.1% AC-24,055, more than 90% suppression of both amylase and protease activity was obtained, whereas at some lower concentrations a slight increase in invertase activity, especially after prolonged feeding, was observed. At 0.1% AC-24,055 the inhibition of the proteolytic activity was considerably stronger than it was in starved larvae. These results suggest that the inhibitory effect on the digestive enzymes is due not only to starvation but also to the effect of the antifeedant. Protease and amylase inhibition was obtained also by injecting AC-24,055 into the larval hemolymph. Maximum inhibition of both amylase and protease, about 50% and 25%, respectively, was reached 2 days after an injection of 5 μg AC-24,055; it then decreased gradually and was abolished 4 days after injection. Adding massive doses of AC-24,055 to the enzyme reaction mixture did not affect the in vitro activity of protease, amylase, or invertase. This indicates that AC-24,055 affects the digestive enzymes indirectly, probably by inhibiting a physiological system affecting the production of these enzymes. © 1974.
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