Biochemical characterization of digestive carbohydrases in the rose sawfly, Arge rosae Linnaeus (Hymenoptera: Argidae)

The rose sawfly, Arge rosae Linnaeus, is one of the most destructive pests of rose bushes in the north of Iran. Nowadays, many attempts have been made to reduce pesticide application by looking for new methods of pest control. A non chemical method for controlling insect pests including A. rosae can be achieved by using genetically engineered plants expressing carbohydrase inhibitors. Therefore, in present study we characterized biochemical properties of digestive carbohydrases in the gut of A. rosae for achieving a new method for control of this pest. The specific activity of α-amylase in the digestive system of last larval instars of A. rosae was obtained as ۹.۴۶ ± ۰.۰۶ μmol min-۱ mg-۱ protein. Also, the optimal pH and temperature for α-amylase were found to be at pH ۸ and ۵۰ °C. As calculated from Lineweaver-Burk plots, the Km and Vmaxvalues for α-amylase were ۰.۸۲ mg/ml and ۷.۳۲ µmol min-۱ mg-۱ protein, respectively, when starch was used as substrate. The effects of ions on amylolytic activity showed that Mg۲+ and Na+ significantly increased amylase activity, whereas SDS and EDTA decreased the enzyme activity. The highest activities of α-/β-glucosidase and β-galactosidase were obtained at pH ۵.۰. By the native PAGE, three, one, one and two bands were clearly detected for α-amylase, α-/β-glucosidase and β-galactosidase, respectively. No bands were found for α-galactosidase that confirmed the absence or low activity of this carbohydrate in the digestive system of A. rosae. These results could provide the knowledge needed to produce transgenic plants for control of this pest.