Carbohydrase activities in the larval digestive system of the cigarette beetle, Lasioderma serricorne (Col.: Anobiidae)

The cigarette beetle, Lasioderma serricorne, is a serious infesting pest of warehouses and retail stores thorough the world. Partial biochemical characterization of carbohydrases was performed in the larval digestive system of the pest. Midgut extracts from larvae showed an optimum activity for
-glucosidase, -glucosidase and
-amylase activity against, p-nitrophenyl-
-D glucopyranoside, p-nitrophenyl-- D-glucopyranoside and starch at pH 5, pH 6 and pH 7, respectively. Larval midgut
-glucosidase was more stable in acidic conditions (pH 4 to pH 6.0) than highly acidic and alkaline conditions. However, the enzyme showed to be more stable in slightly acidic condition (pH 5) when incubation time was increased. -Glucosidase was also stable in acidic conditions (pH 5 to pH 7) and its maximum stability occurred at pH 6. The range of stability for
-amylase was determined in slightly acidic to weakly alkaline conditions (pH 6 to pH 8). Maximum activity for
-glucosidase, -glucosidase and
-amylase incubated at different temperatures was observed at 35, 40 and 50°C, respectively. The KM and Vmax values for
-glucosidase and -glucosidase were 2.77 mM and 0.017 mmol min-1 mg-1 protein and 0.6961 mM and 0.0004 mmol min-1 mg-1 proteins, respectively. The KM and Vmax values for
-amylase were 3.2 mg ml-1 and 0.01 mmol min-1 mg-1 protein. Zymogram analysis revealed the presence of one band of
-amylase activity, one band for each
-glucosidase and  glucosidase activity in the larval midgut extract.