Digestive Carbohydrases in the Larva of the Leopard Moth, Zeuzera pyrina (Lep.: Cossidae)

The leopard moth, Zeuzera pyrina, is a key and worldwide pest damaging walnut as well as many other fruit trees during the larval stages. Larvae were collected from infested twigs of walnut trees. Midguts from larvae were removed under a stereomicroscope and their homogenates used as the enzyme source. Larval midgut extracts showed an optimum activity at pH 8.0, 6.0 and 6.0 for α-amylase, α- and β-glucosidase respectively. Optimal temperatures for α-amylase, α- and β-glucosidase activity were determined to be 35, 35 and 40 ºC respectively. α-Amylase, α- and β-glucosidase were respectively more stable at pHs 7.0-9.0, 6.0-8.0 and 6.0-8.0. However, the enzymes showed to be more stable at pH 8.0 (α-amylase) and 6.0 (α- and β-glucosidase). β-Glucosidase activity significantly decreased in the presence of Ca2+, and sodium dodecyl sulfate (SDS). Ca2+ decreased activity of α-glucosidase as well. The ions K+ and Na+ did not significantly affect the β-glucosidase activity but increased the activity of α-glucosidase. SDS decreased α-glucosidase activity at higher concentrations. Ca2+ and K+ significantly increased the activity of α-amylase. SDS significantly affected α-amylase activity. PAGE-substrate experiments on larval midgut extract showed two bands of α-amylase and one band of each α- and β-glucosidase activity. It is hoped that these findings help to plan strategies for creating transgenic plants resistant to provide the healthy controls.