Carboxylamidase Activity in the Fall Armyworm (Lepidoptera: Noctuidae) and Other Lepidoptera, Orthoptera, and Dictyoptera
Authors: YU, SIMON J.; VALLES, STEVEN M.
Source: Journal of Economic Entomology, Volume 90, Number 6, December 1997 , pp. 1521-1527(7)
Publisher: Entomological Society of America
Abstract:Carboxylamidase activity in larvae of the fall armyworm, Spodoptera frugiperda (J. E. Smith), was studied using p-nitroacetanilide as a model substrate. Enzyme activity was found in all tissues examined, with the midgut exhibiting the highest specific activity. Of the midgut subcellular fractions, the microsomal fraction contained the highest specific activity. The apparent Km value for the enzyme was 0.67 mM and the pH optimum was 8.0. The enzyme was quite stable, losing <10% of its original activity after 10 wk at -20°C. Activity was inhibited in vitro by the hydrolase inhibitors paraoxon, triphenyl phosphate, eserine, and phenylmethyl-sulfonyl fluoride, showing I50 values of 2.8 M, 0.19 mM, 24 M, and 0.13 mM, respectively. Activity was also inhibited by several organophosphorus insecticides at 0.1 mM; profenofos inhibited the enzyme 93%, dichlorvos 94%, and tetrachlorvinphos 75%. Carboxylamidase activity was expressed in all postembryonic stages. It was widely distributed in different insect species from the orders Lepidoptera, Orthoptera, and Dictyoptera. In the cockroach species studied, activity appeared to be family dependent. Activity was highest among the Blattellidae, intermediait' among the Blaberidae, and not detectable in the Blattidae. Carboxylamidase activity toward other aromatic amides such as acetanilide and phenacetin was also detected in fall armyworm larvae.
Document Type: Research Article
Publication date: December 1997
- Journal of Economic Entomology is published bimonthly in February, April, June, August, October, and December. The journal publishes articles on the economic significance of insects and is divided into the following sections: apiculture & social insects; arthropods in relation to plant disease; forum; insecticide resistance and resistance management; ecotoxicology; biological and microbial control; ecology and behavior; sampling and biostatistics; household and structural insects; medical entomology; molecular entomology; veterinary entomology; forest entomology; horticultural entomology; field and forage crops, and small grains; stored-product; commodity treatment and quarantine entomology; and plant resistance. In addition to research papers, Journal of Economic Entomology publishes Letters to the Editor, interpretive articles in a Forum section, Short Communications, Rapid Communications, and Book Reviews.
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