Esterases from Lygus hesperus Knight and their roles in insecticide resistance were studied with field populations. The esterases are B-type esterases; carboxyl esterases are predominant in susceptible (S)and resistant (R)populations. The optimal pH and temperature were 7.8-8.0 and 40-45°C, respectively. Km(Michaelisconstant) determined with I-naphthyl acetate at 43°C was similar in the Sand R populations; it was 8.8 x 10-6 M for males and 1.3 x 10-' M for females. Vmax (maximal velocity) was 27.0 and I36.Iltmol/min per mg protein for the Sand R populations, respectively. The esterases in the R population did not differ from the esterases in the S population, either in response to inhibition by eserine, paraoxon, or trichlorfon or in affinity to substrate (I-naphthyl acetate). However, esterase activity was 4.2 to 6.1 times greater in the R population than in the S population. These results suggest that there are quantitative rather than qualitative differences between the two populations. The greatly increased activity in the R population is apparently due to the production of more carboxyl esterases, which may play an important role in insecticide resistance.
Document Type: Research Article
Publication date: June 1, 1990
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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.