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Esterase
About: Esterase is a research topic. Over the lifetime, 7622 publications have been published within this topic receiving 168270 citations.
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TL;DR: These findings, and the linkage disequilibrium of the kdr mutation within clones overproducing the E4 esterase, have important implications for the evolution of resistance in this insect and for the use of pyrethroid sprays in the management of M. persicae populations in the field.
Abstract: The voltage-gated sodium channel is the primary target site of DDT and pyrethroid insecticides, and point mutations in the domain II region of the channel protein have been implicated in the knockdown resistant (kdr ) phenotype of several insect species. Here, we report that one of these mutations, a leucine-to-phenylalanine replacement in transmembrane segment IIS6, is also found in certain insecticide-resistant clones of the peach-potato aphid, Myzus persicae. The mutation was present in four clones with amplified E4 esterase genes, but was absent from both susceptible clones and those with amplified FE4 genes. The inferred presence of kdr-type resistance in the four E4 clones was subsequently confirmed by bioassays that showed this to be the primary mechanism of resistance to deltamethrin and DDT, although the esterase-based mechanism also contributes to the overall level of deltamethrin resistance. The kdr mutation on its own conferred 35-fold resistance to deltamethrin and this was enhanced up to 540-fold when it was present in a high (E4) esterase background. The esterase (FE4) mechanism was far less effective without the kdr mutation, conferring just 3-4-fold resistance to deltamethrin. These findings, and the linkage disequilibrium of the kdr mutation within clones overproducing the E4 esterase, have important implications for the evolution of resistance in this insect and for the use of pyrethroid sprays in the management of M. persicae populations in the field.
202 citations
TL;DR: In order to determine more precisely the specificity of these two enzymes with regard to short and long chain fatty acid esters and their relationship to certain enzymatic inhibitors and activators, the &naphthyl esters of acetic (CJ, lauric (C&J, and palmitic-stearic) acids were prepared as substrates.
199 citations
TL;DR: The results indicated that the insecticide resistance observed in the field strain was due to multiple resistance mechanisms, including increased detoxification of these insecticides by microsomal oxidases, glutathione S -transferases, hydrolases and reductases, and target site insensitivity such as insensitive acetylcholinesterase.
197 citations
TL;DR: Cl cloning and characterisation of the orthologous M. domestica Md alpha E7 gene are reported, including the sequencing of cDNAs from the OP resistant Rutgers and OP susceptible sbo and WHO strains, and identical catalytic mechanisms have evolved in Orthologous Mdalpha E7 and LcAlpha E7 molecules to endow diazinon-type resistance on the two species of higher Diptera.
195 citations
TL;DR: This chapter presents the sequence studies of peptides and proteins using carboxypeptidase Y, an enzyme that removes amino acids as one residue at a time from the carboxyl termini of proteins and peptides.
Abstract: Publisher Summary Carboxypeptidase Y is an enzyme that removes amino acids as one residue at a time from the carboxyl termini of proteins and peptides. This chapter presents the sequence studies of peptides and proteins using carboxypeptidase Y. The assay of peptidase activity is based on the rate of the enzymic hydrolysis of benzyloxycarbonyl-L-phenylalanyl-L-leucine (Z-Phe-Leu). The rate of the reaction can be measured either with the colorimetric ninhydrin method for the estimation of liberated leucine, or spectrophotometrically by the decreases in absorbance at 224 nm. The assay of esterase activity is based on the titrimetric measurement of the release of protons, or upon the spectrophotometric measurement of the change in ultraviolet absorbancy that occurs as a result of the enzymic hydrolysis of Ac-Tyr-OEt. It is found that carboxypeptidase Y hydrolyzes ester and amide substrates of chymotrypsin. The properties of amidase action could be applied to the sequence analyses of peptides with amidated COOH-terminal groups, such as oxytocin and vasopressin.
194 citations