Riseh N.S., Ghadamyari M., Motamediniya B. (2012): Biochemical characterisation of α-and β-glucosidases and α-and β-galactosidases from red palm weevil, Rhynchophorus ferrugineus (Olivier) (Col.: Curculionide). Plant Protect. Sci., 48: 85-93.The red palm weevil, Rhynchophorus ferrugineus (Olivier), is one of the most destructive pests of palm trees in the southeast of Iran. Digestion in the alimentary canal of the red palm weevil is facilitated by some carbohydrases. Results of the in vitro studies indicated the presence of α-and β-glucosidases and α-and β-galactosidases in the digestive system and haemolymph of this pest. In the digestive system of females, the activities of α-glucosidase and β-galactosidase were higher than those of β-glucosidase and α-galactosidase. Also, the specific activity of α-and β-glucosidases and α-and β-galactosidases in the female digestive system was much higher than that in larvae. Results showed that the highest activities of α-and β-glucosidases were at pH 5 and of α-and β-galactosidases at pH 4. The R. ferrugineus α-and β-glucosidases and α-and β-galactosidases have an optimum temperature activity at 50, 50-60, 40-60, and 40°C, respectively. A zymogram pattern in the native gel revealed that R. ferrugineus α-and β-glucosidases and α-and β-galactosidases in the digestive system showed 2, 3, 1 and 1 major bands, respectively. The activity of α-glucosidase in the digestive system of larvae and female adults was higher than that of the other carbohydrases. Therefore, it is the most important subject for further study and design of a new approach to the control of this pest using carbohydrase inhibitors.

Proteases are one of the most important digestive enzymes in the midgut of Hyphantria cunea Drury. Proteases are responsible for protein digestion. In the present study, we evaluated the efficiency of some plant inhibitors on proteases in the gut of the H. cunea. Last instar larvae were collected from mulberry trees. The digestive system of the larvae was used as an enzyme source. The total proteolytic and trypsin activity were assessed by the hemoglobin and BApNA, respectively, as the substrate. The evaluation of the total proteolytic and trypsin activities in various pHs showed the highest relative activity at a pH of 11. Also, the inhibitory effect of inhibitors extracted from Alhagi maurorum Medik., Lathyrus sativus L., Vicia faba L., Prosopis farcta (Banks & Sol.) Eig., and Panicum miliaceum L. on the digestive protease of the fall webworm was measured. Protease inhibitors extracted from A. maurorum, P. farcta and P. miliaceum showed negligible inhibition but L. sativus was able to inhibit 34.72% and 100% of the total activity of proteolytic and trypsin, respectively. Also, the total proteolytic and trypsin activities were inhibited by the inhibitor from V. faba, at 22.27% and 100%, respectively. The zymogram pattern of trypsin with nitro-cellulose membranes showed 2 isoforms in the gut of H. cunea. The inhibitor from L. sativus completely inhibited both isoforms. Gel electrophoresis of proteolitytic activity revealed at least 6 isoforms the inhibitor extracted from L. sativus; completely inhibiting some of them. The inhibitor from L. sativus was purified by ammonium sulfate precipitation and gel-filtration. The molecular mass of the inhibitor was determined as 45 kDa. The highest inhibition of trypsin activity by the inhibitor from L. sativus occurred at a pH of 10. The stability of the inhibitor from L. sativus was evaluated at different pHs and temperatures. The results showed that the inhibitor from L. sativus was stable at a pH of 11.0, and showed 45% inhibition on trypsin activity at a pH of 11. Also, this inhibitor revealed stability up to 50°C.