digestive amylase and glucosidases in the larval stage of elm leaf beetle, xanthogaleruca luteola (col.: chrysomelidae)

elm leaf beetle, xanthogaleruca luteola, is a serious pest (particularly at its larval stage) of elm trees in many areas. the existence of three important enzyms namely: ?-amylase, ?- glucosidase and ?-glucosidase in the midgut of the insect at its larval stage was investigated. optimum activity for ?-, ?-glucosidase and ?-amylase was recorded at phs 5.0, 6.0 and 6.0 against p-nitrophenyl-?-d-glucopyranoside, p-nitrophenyl-?-d-glucopyranoside and starch respectively. ? and ?-glucosidase exhibited more stability at phs 4.0-6.0 than at either highly acidic or and alkaline phs. these enzymes were respectively more stable at ph 5.0 and 6.0 with increased incubation time. ? -amylase was stable at phs 4.0-8.0. ? and ?-glucosidase and also ?-amylase, when incubated at different temperatures were found to be maximally active at 45, 60 and 40°c, respectively. alpha- glucosidase activity significantly decreased in the presence of ca2+ and mg2+. on the contrary, the ions k+ and na+ did not significantly affect the enzyme’s activity. the ions k+, mg2+ and na+ did not significantly affect the enzyme activity. zymogram analysis revealed the presence of one band each of amylase, ?- and ?-glucosidase activity in the insect’s larval midgut extract.