Lipase and invertase activities in midgut and salivary glands of Chilo suppressalis (Walker) (Lepidoptera, Pyralidae), rice striped stem borer [For this article an Erratum has been published]

Abstract

The rice striped stem borer, Chilo supprressalis, was introduced to Iran in 1973 where it is now
widely distributed and causes severe damages. Lipases, which catalyses the hydrolysis of fatty acid
ester bonds, are widely distributed among animals, plants and microorganisms. Invertases (β-
fructofuranosidase) are glycosidehydrolases that catalyze the cleavage of sucrose (β-Dglucopyranosyl-S-D-fructofuranoside) into the monosaccharides glucose and fructose. Laboratoryreared 4th instar larvae were randomly selected, their midgut and salivary glands were removed by dissection under a light microscope and lipase and invertase activities were assayed. The activity of lipase/invertase in the midgut and salivary gland were 0.49/0.27 and 0.35/0.23 µmol/min/mg protein, respectively. The optimum pH and temperature for both the two enzymes were determined to be 10- 11 and 37-40 °C, which is consistent with pH and temperature values already observed in Lepidoptera. The enzyme activity was reduced by addition of NaCl, KCl, MgCl2, SDS, urea and plant extracts from Artemisia annua, but not by CaCl2 which enhanced enzyme activity. Pest control with usage of resistant varieties of plants is one of the most important practices that are dependant on inhibitors already present in nature. Hence, characterization of insect digestive enzymes, especially examination of inhibition effects on enzyme activity, could be useful in developing new strategies for pest control.