@article{kao_motoyama_dauterman_1985, title={THE PURIFICATION AND CHARACTERIZATION OF ESTERASES FROM INSECTICIDE-RESISTANT AND SUSCEPTIBLE HOUSE-FLIES}, volume={23}, ISSN={["1095-9939"]}, DOI={10.1016/0048-3575(85)90010-0}, abstractNote={Four major esterases in one susceptible (CSMA) and two resistant (Hirokawa, E1) house fly strains were separated by chromatofocusing. Of the four esterases, those with pI's of 5.1 and 5.3 accounted for 90% of the p-nitrophenyl butyrate hydrolyzing activity in the three house fly strains. They also accounted for 70% (Hirokawa, E1) and 40% (CSMA) of the paraoxon-hydrolyzing activity as well as 87% (Hirokawa), 39% (E1) and 66% (CSMA) of the malathion-hydrolyzing activity in microsomes as measured by esterase-antibody interaction. In the Hirokawa strain, the pI 5.1 esterase was the predominant esterase and was more active than that of the the CSMA strain. Different substrate specificities and a different Km toward acetylthiocholine, as well as different rates of malathion and paraoxon hydrolysis between the Hirokawa and CSMA strains, suggest a qualitative difference in the pI 5.1 esterase. For the pI 5.1 esterase from the E1 strain, a different substrate specificity, a different Km for p-nitrophenyl butyrate, a different sensitivity to inhibitors, and a different rate of paraoxon hydrolysis suggest that it is a modified esterase. This esterase is not a phosphorotriester hydrolase, nor does it lack nonspecific esterase activity. It is a modified esterase which has a different substrate specificity when compared to the esterases from the other strains. The molecular weight of the esterases studied was approximately 220,000, with pH optima of about 7.0. The ratio of malathion α-monoacid to β-monoacid formation was about 9.0 for the pI 5.1 and 5.3 esterases and 1.5 for the pI 4.8 and 5.6 esterases. The existence of a higher αβ ratio for the pI 5.1 and 5.3 esterases and their significant rate of malathion hydrolysis in the Hirokawa strain indicate that an increase in the αβ ratio in house flies reported was due to the increase in the pI 5.1 esterase in the resistant strain.}, number={2}, journal={PESTICIDE BIOCHEMISTRY AND PHYSIOLOGY}, author={KAO, LR and MOTOYAMA, N and DAUTERMAN, WC}, year={1985}, pages={228–239} }
 @article{kao_motoyama_dauterman_1984, title={STUDIES ON HYDROLASES IN VARIOUS HOUSEFLY STRAINS AND THEIR ROLE IN MALATHION RESISTANCE}, volume={22}, ISSN={["1095-9939"]}, DOI={10.1016/0048-3575(84)90013-0}, abstractNote={Aliesterase, carboxylesterase, and phosphorotriester hydrolase activities in six house fly strains were studied in relation to malathion resistance. Selection of two susceptible strains with malathion for three generations resulted in an increase in both carboxylesterase activity and LD50 of malathion, indicating that the increased detoxication by the enzyme was the major mechanism selected for malathion resistance. With the highly resistant strains, however, the carboxylesterase activity alone was not sufficient to explain the resistance level, and the involvement of additional mechanisms, including phosphorotriester hydrolase activity, was suggested. The E1 strain, which had high phosphorotriester hydrolase activity but normal or low carboxylesterase activity, showed a moderate level, i.e., sevenfold resistance. Upon DEAE-cellulose chromatography, two or three esterase peaks were resolved from susceptible, moderately resistant, and highly resistant strains. The substrate specificity, the sensitivity to paraoxon inhibition, and the αβ ratio of malathion hydrolysis were studied for each esterase peak from the different strains. The results suggested the existence of multiple forms of esterases with overlapping substrate specificity in the house fly.}, number={1}, journal={PESTICIDE BIOCHEMISTRY AND PHYSIOLOGY}, author={KAO, LR and MOTOYAMA, N and DAUTERMAN, WC}, year={1984}, pages={86–92} }