Entomology, Department of


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Published in Ann. Entomol. Soc. Am. 92(4): 556-562 (1999) Copyright 1999 Entomological Society of America Used by Permission


The distribution and inhibition of esterase activity among body of the resistant Crawford and susceptible CSMA strains of male German cockroach, Blattella germanica (L.), were evaluated with α- and β-naphthyl esters using a spectrophotometric assay and native polyacrylamide gel electrophoresis. The esterase activities in the Crawford strain were significantly higher than in the CSMA strain in most tissues except midgut and male genitalia, where the activities were similar. In both strains, isozyme a was dominant in the brain and fat body and isozymes c and d were more abundant in the midgut; but in addition to isozyme a, isozyme b was observed only in the Crawford strain. The α-naphthyl butyrate (α-NB) and β-naphthyl acetate (β-NA) esterase activities in the brain of both strains were completely inhibited by most inhibitors (DEF, 3,4-dichloroisocoumarine, paraoxon, pepstatin A, and propoxur). However, in the midgut tissue and contents, the activities and inhibition patterns of the α-NB and β-NA esterase were apparently different from the brain and between strains.The complete inhibition by paraoxon was observed regardless of the strain, substrate type, and body part for enzyme source. In esterase inhibition on native PAGE gels, paraoxon completely inhibited the activity of most esterases similar to the results from spectrophotometric assay. In addition, the esterase b was observed from the whole body homogenates of several German cockroach resistant strains on native PAGE analysis.

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