Arthropods (Sep 2013)
Biochemical properties of digestive carbohydrases from the sugar beet weevil, Lixus incanescens (Coleoptera: Curculionidae)
Abstract
The sugar beet weevil, Lixus incanescens B., is one of the most important pests of sugar beet plant in Iran. The petioles and leaves of sugar beet are attacked by larvae and adults of the sugar beet weevil. Chemical application is currently used for controlling the pest. Digestion in the alimentary canal of the sugar beet weevil is facilitated by some carbohydrases. Results of the in vitro studies indicated the presence of alpha-amylase, beta-glucosidase and beta-galactosidase in the digestive tract of the pest. Highest activities of alpha-amylase, beta-glucosidase and beta-galactosidase were at pH 5, pH 5 and pH 4, respectively. No significant alpha-glucosidase and alpha-galactosidase activity was detected in the pest's digestive system. Optimum temperatures for alpha-amylase, beta-glucosidase and beta-galactosidase activity were determined at 45, 50 and 40 oC, respectively. alpha-amylase was more stable under acidic condition (pH 4 to pH 6) than under highly acidic and alkaline condition. Na+ and K+ increased alpha-amylase activity, but sodium dodecyl sulfate significantly decreased amylase activity. Also, the activity of alpha-amylase was inhibited by the other compounds such as MgCl2, CaCl2 and EDTA. Zymogram analysis using native-PAGE revealed one band of alpha-amylase activity in Lixus incanescens. High activity of carbohydrases in the digestive system of adults was determined and further researches are needed to be applied to design new strategies for controlling the sugar beet weevil based on natural carbohydrase inhibitors.
