| The participation of esterases in the detoxification process is only one of the adaptation mechanisms of insects in order to survive the lethality of chemical compounds. During the evolutionary process, the metabolic pathways of arthropods and their metabolic capacity has been strengthened in order to deal with a broad number of toxic compounds, for example pyrethroids, produced by plants, some of them very related to those pyrethroids actually used to control some pests. The presence of esterases is one of the most important mechanisms of resistance in several insect species. Overexpressed esterases have been associated with pesticide resistance. Boophilus microplus tick larvae have shown the presence of a highly active alpha-esterase of approximately 67 KDa probably associated with resistance. The analysis of the sequences of the esterases in the case of B. microplus is a very important issue in trying to understand the role of the esterases in the resistance phenomenon and getting a new diagnostic tool to circumvent the inconveniences of the current methodology used for diagnosis of resistance. Differential overexpression of esterase activity has been found in resistant strains and also a fragment of an esterase DNA has been amplified by Polymerase Chain Reaction by using degenerate primers derived from the alignments of related esterases and cloned into a TOPO TA Cloning vectorTM. The sequence was analyzed by using the computer program BLAST (Basic Local Alignments Search Tools) provided by the National Institute for Biotechnology Information and the analysis showed a high homology (55% homology) with the amino acid sequences of other acetylcholinesterases. The conserved sequences of the active site EDCLYLN and FGESAG used as primers were not included in the analysis. |
