Genetic and biochemical studies of the highly active esterases A? and B associated with organophosphate resistance in mosquitoes of the Culex pipiens complex

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Abstract
The highly active esterases A′ and B that cannot be dissociated from OP resistance in Culex pipiens from France and California are shown to have equivalent K m values (2.1×10−6 m/min/mosquito) but different turnover rates (V m =2.13 and 0.57×10−6 m/min/mosquito, respectively) and pH for maximum activity. Both enzymes have broad substrate specificities and at least one, esterase A′, can hydrolyze OP insecticides. In addition, esterases A′ and B are coded by two closely linked genes, Est-3 and Est-2, respectively (0.67 unit of crossing over), located on the same autosome as pl, a locus attributed to linkage group III. The estimated distance between Est-2 and pl was 9.4 units.