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ARS Home » Southeast Area » Gainesville, Florida » Center for Medical, Agricultural and Veterinary Entomology » Imported Fire Ant and Household Insects Research » Research » Publications at this Location » Publication #76190
Title: CARBOXYLAMIDASE IN THE FALL ARMYWORM, SPODOPTERA FRUGIPERDA, AND COMPARITIVE ACTIVITIES IN OTHER LEPIDOPTERA, ORTHOPTERA AND DICTYOPTERA

Author
item YU, SIMON - UNIV FLORIDA
item Valles, Steven

Submitted to: Archives of Insect Biochemistry and Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/16/1997
Publication Date: N/A
Citation: N/A

Interpretive Summary: The major mechanism responsible for insecticide resistance in insects is enhanced detoxification. Insecticides are degraded to non-toxic chemicals by specific enzymes in various tissues of the insect. Scientists at the University of Florida and the USDA-ARS, Center for Medical, Agricultural and Veterinary Entomology characterized one of these enzymes (amidase) in several moth and cockroach species. These results provide the basis for future investigations into the mechanisms of insecticide resistance and the role amidases play in the detoxification of certain insecticides.

Technical Abstract: Carboxylamidase 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 michaelis constant value for the enzyme was 0.67 mM and the pH optimum was 8.0. The enzyme was quite stable, losing less than 10 percent of its original activity after ten weeks at -20 degrees C. Activity was inhibited in vitro by the hydrolase inhibitors paraoxon, O,O,O-triphenyl phosphate, eserine and phenylmethylsulfonyl fluoride, showing 50 percent inhibition values of 2.8 yM, 0.19 mM, 24 yM and 0.13 mM, respectively. Activity was also inhibited by several organophosphorus insecticides at 0.1 mM; profenofos inhibited the enzyme 93 percent, dichlorvos 94 percent, and tetrachlorvinphos 75 percent. Carboxylamidase activity was expressed in all developmental 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, intermediate among the Blaberidae and not detectable in the Blattidae.