CHARACTERIZATION OF A B-TYPE ESTERASE INVOLVED IN INSECTICIDE RESISTANCE FROM THE MOSQUITO CULEX-QUINQUEFASCIATUS

The enzyme, esterase B2, involved in insecticide resistance has been p urified and characterized from the mosquito Culex quinque-fasciatus. T he monomeric enzyme has an M(r) of 62000 and a pI of 5.0. This enzyme is compared with the esterase A2 previously characterized [Ketterman, Jayawardena and Remingway (1992) Biochem. J. 287, 355-360]. The kineti c constants for interaction with several insecticides indicate, as for the esterase A2, that the B2 enzyme has a role in resistance. The rat es and affinities of binding observed support the hypothesis that the role mainly is sequestration followed by the slow turnover of the inse ctide. Although the B2 esterase appears to have a slightly higher rate of interaction with insecticides, the A2 has a much greater V(max) wi th the xenobiotic substrates studied. The B2 esterase also appears to be present in the larvae to a lesser extent than the esterase A2.