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Carboxylesterase Activity (carboxylesterase + activity)
Selected AbstractsDevelopment of toxicity identification evaluation procedures for pyrethroid detection using esterase activityENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 11 2004Craig E. Wheelock Abstract Recent agrochemical usage patterns suggest that the use of organophosphate (OP) pesticides will decrease, resulting in a concomitant increase in pyrethroid usage. Pyrethroids are known for their potential toxicity to aquatic invertebrates and many fish species. Current toxicity identification evaluation (TIE) techniques are able to detect OPs, but have not been optimized for pyrethroids. Organophosphate identification methods depend upon the use of piperonyl butoxide (PBO) to identify OP-induced toxicity. However, the use of PBO in TIE assays will be confounded by the co-occurrence of OPs and pyrethroids in receiving waters. It is necessary, therefore, to develop new TIE procedures for pyrethroids. This study evaluated the use of a pyrethroid-specific antibody, PBO, and carboxylesterase activity to identify pyrethroid toxicity in aquatic toxicity testing with Ceriodaphnia dubia. The antibody caused significant mortality to the C. dubia. Piperonyl butoxide synergized pyrethroid-associated toxicity, but this effect may be difficult to interpret in the presence of OPs and pyrethroids. Carboxylesterase activity removed pyrethroid-associated toxicity in a dose-dependent manner and did not compromise OP toxicity, suggesting that carboxylesterase treatment will not interfere with TIE OP detection methods. These results indicate that the addition of carboxylesterase to TIE procedures can be used to detect pyrethroids in aquatic samples. [source] Molecular characterization of the amplified carboxylesterase gene associated with organophosphorus insecticide resistance in the brown planthopper, Nilaparvata lugensINSECT MOLECULAR BIOLOGY, Issue 6 2000Graham J. Small Abstract Widespread resistance to organophosphorus insecticides (OPs) in Nilaparvata lugens is associated with elevation of carboxylesterase activity. A cDNA encoding a carboxylesterase, Nl-EST1, has been isolated from an OP-resistant Sri Lankan strain of N. lugens. The full-length cDNA codes for a 547-amino acid protein with high homology to other esterases/lipases. Nl-EST1 has an N-terminal hydrophobic signal peptide sequence of 24 amino acids which suggests that the mature protein is secreted from cells expressing it. The nucleotide sequence of the homologue of Nl-EST1 in an OP-susceptible, low esterase Sri Lankan strain of N. lugens is identical to Nl-EST1. Southern analysis of genomic DNA from the Sri Lankan OP-resistant and susceptible strains suggests that Nl-EST1 is amplified in the resistant strain. Therefore, resistance to OPs in the Sri Lankan strain is through amplification of a gene identical to that found in the susceptible strain. [source] Newly isolated Streptomyces spp. as enantioselective biocatalysts: hydrolysis of 1,2-O-isopropylidene glycerol racemic estersJOURNAL OF APPLIED MICROBIOLOGY, Issue 4 2005F. Molinari Abstract Aims:, To identify microbial strains with esterase activity able to enantioselectively hydrolyse esters of (R,S)-1,2-O-isopropylidene glycerol. Methods and Results:, The microbial hydrolysis of various racemic esters of 1,2-O-isopropylidene glycerol (IPG) was attempted by screening among Streptomyces spp. previously selected on the basis of their carboxylesterase activity. The best results were observed in the hydrolysis of butyrate ester and two strains appeared promising as they showed opposite enantioselectivity: Streptomyces sp. 90852 gave predominantly (S)-IPG, while strain 90930 mostly gave the R -alcohol. Streptomyces sp. 90930 was identified as Streptomyces violaceusniger, whereas Streptomyces sp. 90852 is a new species belonging to the Streptomyces violaceus taxon. The carboxylesterase belonging to strain 90852 gave a maximum value of enantiomeric ratio (E) of 14,16. This strain was lyophilized and used as dry mycelium for catalysing the synthesis of isopropylidene glycerol butyrate in heptane showing reaction rate and enantioselectivity (E = 6·6) lower than what observed for the hydrolysis. Conclusions:, A new esterase with enantioselective activity towards (R,S)-IPG butyrate has been selected. The best enantioselectivity is similar or even better than the highest reported value in the literature with commercial enzymes. The enzyme is produced by a new species belonging to the S. violaceus taxon. Significance and Impact of the Study:, New esterases from streptomycetes can be employed for the enantioselective hydrolysis of chiral esters derived from primary alcohols, not efficiently resolved with commercial enzymes. [source] Pyrethroid and DDT cross-resistance in Aedes aegypti is correlated with novel mutations in the voltage-gated sodium channel geneMEDICAL AND VETERINARY ENTOMOLOGY, Issue 1 2003C. Brengues Abstract. Samples of the dengue vector mosquito Aedes aegypti (L.) (Diptera: Culicidae) were collected from 13 localities between 1995 and 1998. Two laboratory strains, Bora (French Polynesia) and AEAE, were both susceptible to DDT and permethrin; all other strains, except Larentuka (Indonesia) and Bouaké (Ivory Coast), contained individual fourth-instar larvae resistant to permethrin. Ten strains were subjected to a range of biochemical assays. Many strains had elevated carboxylesterase activity compared to the Bora strain; this was particularly high in the Indonesian strains Salatiga and Semarang, and in the Guyane strain (Cayenne). Monooxygenase levels were increased in the Salatiga and Paea (Polynesia) strains, and reduced in the two Thai strains (Mae Kaza, Mae Kud) and the Larentuka strain. Glutathione S-transferase activity was elevated in the Guyane strain. All other enzyme profiles were similar to the susceptible strain. The presence of both DDT and pyrethroid resistance in the Semarang, Belem (Brazil) and Long Hoa (Vietnam) strains suggested the presence of a knock-down resistant (kdr)-type resistance mechanism. Part of the S6 hydrophobic segment of domain II of the voltage-gated sodium channel gene was obtained by RT-PCR and sequenced from several insects from all 13 field strains. Four novel mutations were identified. Three strains contained identical amino acid substitutions at two positions, two strains shared a different substitution, and one strain was homozygous for a fourth alteration. The leucine to phenylalanine substitution that confers nerve insensitivity to pyrethroids in a range of other resistant insects was absent. Direct neurophysiological assays on individual larvae from three strains with these mutations demonstrated reduced nerve sensitivity to permethrin or lambda cyhalothrin inhibition compared to the susceptible strains. [source] Cross-resistance study and biochemical mechanisms of thiamethoxam resistance in B-biotype Bemisia tabaci (Hemiptera: Aleyrodidae)PEST MANAGEMENT SCIENCE (FORMERLY: PESTICIDE SCIENCE), Issue 3 2010Yuntao Feng Abstract BACKGROUND: B-biotype Bemisia tabaci (Gennadius) has invaded China over the past two decades. To understand the risks and to determine possible mechanisms of resistance to thiamethoxam in B. tabaci, a resistant strain was selected in the laboratory. Cross-resistance and the biochemical mechanisms of thiamethoxam resistance were investigated in the present study. RESULTS: A 66.3-fold thiamethoxam-resistant B. tabaci strain (TH-R) was established after selection for 36 generations. Compared with the susceptible strain (TH-S), the selected TH-R strain showed obvious cross-resistance to imidacloprid (47.3-fold), acetamiprid (35.8-fold), nitenpyram (9.99-fold), abamectin (5.33-fold) and carbosulfan (4.43-fold). No cross-resistance to fipronil, chlorpyrifos or deltamethrin was seen. Piperonyl butoxide (PBO) and triphenyl phosphate (TPP) exhibited significant synergism on thiamethoxam effects in the TH-R strain (3.14- and 2.37-fold respectively). However, diethyl maleate (DEM) did not act synergistically with thiamethoxam. Biochemical assays showed that cytochrome P450 monooxygenase activities increased 1.21- and 1.68-fold respectively, and carboxylesterase activity increased 2.96-fold in the TH-R strain. However, no difference was observed for glutathione S -transferase between the two strains. CONCLUSION: B-biotype B. tabaci develops resistance to thiamethoxam. Cytochrome P450 monooxygenase and carboxylesterase appear to be responsible for the resistance. Reasonable resistance management that avoids the use of cross-resistance insecticides may delay the development of resistance to thiamethoxam in this species. Copyright © 2009 Society of Chemical Industry [source] | ||||||||||