scholarly journals Characterization of a B-type esterase involved in insecticide resistance from the mosquito Culex quinquefasciatus

1993 ◽  
Vol 294 (2) ◽  
pp. 575-579 ◽  
Author(s):  
S H P P Karunaratne ◽  
K G Jayawardena ◽  
J Hemingway ◽  
A J Ketterman
Keyword(s):  
Insecticide Resistance ◽  
Culex Quinquefasciatus ◽  
Kinetic Constants ◽  
Slow Turnover

The enzyme, esterase B2, involved in insecticide resistance has been purified and characterized from the mosquito Culex quinquefasciatus. The 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 Hemingway (1992) Biochem. J. 287, 355-360]. The kinetic constants for interaction with several insecticides indicate, as for the esterase A2, that the B2 enzyme has a role in resistance. The rates and affinities of binding observed support the hypothesis that the role mainly is sequestration followed by the slow turnover of the insecticide. Although the B2 esterase appears to have a slightly higher rate of interaction with insecticides, the A2 has a much greater Vmax. with the xenobiotic substrates studied. The B2 esterase also appears to be present in the larvae to a lesser extent than the esterase A2.

scholarly journals Purification and characterization of a carboxylesterase involved in insecticide resistance from the mosquito Culex quinquefasciatus

1992 ◽  
Vol 287 (2) ◽  
pp. 355-360 ◽  
Author(s):  
A J Ketterman ◽  
K G Jayawardena ◽  
J Hemingway
Keyword(s):  
Insecticide Resistance ◽  
Culex Quinquefasciatus ◽  
Minor Role ◽  
Organophosphate Insecticide ◽  
Purification And Characterization ◽  
Medium Chain Length ◽  
A Minor ◽  
Slow Turnover

A carboxylesterase (EC 3.1.1.1) involved in organophosphate insecticide resistance has been purified and characterized from the mosquito Culex quinquefasciatus. The monomeric enzyme has M(r) of 67,000 and a pI of 5.2. It hydrolysed medium-chain-length mono- and di-acylglycerols in addition to xenobiotic esters. Kinetic constants determined for four insecticides, temephos, chlorpyrifos, fenitrothion and propoxur indicate the rates of acylation and the affinities of binding of the insecticides to this carboxylesterase are important. This supports the major role of the A2 carboxylesterase is the sequestration of the insecticide with a minor role in the slow turnover of the insecticide.

scholarly journals Enzymatic Characterization of Insecticide Resistance Mechanisms in Field Populations of Malaysian Culex quinquefasciatus Say (Diptera: Culicidae)

PLoS ONE ◽  
2013 ◽  
Vol 8 (11) ◽  
pp. e79928 ◽  
Author(s):  
Van Lun Low ◽  
Chee Dhang Chen ◽  
Han Lim Lee ◽  
Tiong Kai Tan ◽  
Chin Fong Chen ◽  
...  
Keyword(s):  
Insecticide Resistance ◽  
Culex Quinquefasciatus ◽  
Resistance Mechanisms ◽  
Enzymatic Characterization

scholarly journals A New Ultrasensitive Bioluminescence-Based Method for Assaying Monoacylglycerol Lipase

2021 ◽  
Vol 22 (11) ◽  
pp. 6148
Author(s):  
Matteo Miceli ◽  
Silvana Casati ◽  
Pietro Allevi ◽  
Silvia Berra ◽  
Roberta Ottria ◽  
...  
Keyword(s):  
Arachidonic Acid ◽  
Kinetic Constants ◽  
New Method ◽  
Monoacylglycerol Lipase ◽  
Enzymatic Cleavage ◽  
Highly Sensitive ◽  
Bioluminescence Assay ◽  
Identification And Characterization ◽  
In Cells

A novel bioluminescent Monoacylglycerol lipase (MAGL) substrate 6-O-arachidonoylluciferin, a D-luciferin derivative, was synthesized, physico-chemically characterized, and used as highly sensitive substrate for MAGL in an assay developed for this purpose. We present here a new method based on the enzymatic cleavage of arachidonic acid with luciferin release using human Monoacylglycerol lipase (hMAGL) followed by its reaction with a chimeric luciferase, PLG2, to produce bioluminescence. Enzymatic cleavage of the new substrate by MAGL was demonstrated, and kinetic constants Km and Vmax were determined. 6-O-arachidonoylluciferin has proved to be a highly sensitive substrate for MAGL. The bioluminescence assay (LOD 90 pM, LOQ 300 pM) is much more sensitive and should suffer fewer biological interferences in cells lysate applications than typical fluorometric methods. The assay was validated for the identification and characterization of MAGL modulators using the well-known MAGL inhibitor JZL184. The use of PLG2 displaying distinct bioluminescence color and kinetics may offer a highly desirable opportunity to extend the range of applications to cell-based assays.

scholarly journals High insecticide resistance mediated by different mechanisms in Culex quinquefasciatus populations from the city of Yaoundé, Cameroon

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Abdou Talipouo ◽  
Konstantinos Mavridis ◽  
Elysée Nchoutpouen ◽  
Borel Djiappi-Tchamen ◽  
Emmanouil Alexandros Fotakis ◽  
...  
Keyword(s):  
Insecticide Resistance ◽  
Vector Control ◽  
High Resistance ◽  
Culex Quinquefasciatus ◽  
Control Strategies ◽  
Cuticular Hydrocarbon ◽  
Control Measures ◽  
High Frequencies ◽  
The City ◽  
Integrated Vector Control

AbstractCulex mosquitoes particularly Culex quinquefasciatus are important arboviral and filariasis vectors, however despite this important epidemiological role, there is still a paucity of data on their bionomics. The present study was undertaken to assess the insecticide resistance status of Cx. quinquefasciatus populations from four districts of Yaoundé (Cameroon). All Culex quinquefasciatus populations except one displayed high resistance to bendiocarb and malathion with mortalities ranging from 0 to 89% while high resistance intensity against both permethrin and deltamethrin was recorded. Molecular analyses revealed high frequencies of the ACE-1 G119S mutation (ranging from 0 to 33%) and kdr L1014F allele (ranging from 55 to 74%) in all Cx. quinquefasciatus populations. Significant overexpression was detected for cytochrome P450s genes CYP6AA7 and CYP6Z10, as well as for Esterase A and Esterase B genes. The total cuticular hydrocarbon content, a proxy of cuticular resistance, was significantly increased (compared to the S-lab strain) in one population. The study confirms strong insecticide resistance mediated by different mechanisms in Cx. quinquefasciatus populations from the city of Yaoundé. The expansion of insecticide resistance in Culex populations could affect the effectiveness of current vector control measures and stress the need for the implementation of integrated vector control strategies in urban settings.

Organophosphorus insecticide resistance in a new strain of Culex quinquefasciatus (Diptera: Culicidae) from Tanga, Tanzania

1993 ◽  
Vol 83 (1) ◽  
pp. 67-74 ◽  
Author(s):  
A. Khayrandish ◽  
R.J. Wood
Keyword(s):  
Insecticide Resistance ◽  
Culex Quinquefasciatus ◽  
Gel Electrophoresis ◽  
Polyacrylamide Gel Electrophoresis ◽  
Laboratory Culture ◽  
Fourth Instar ◽  
Resistance Allele ◽  
Susceptible Control ◽  
The Mean

AbstractFourth instar larvae of a new strain of Culex quinquefasciatus Say from Tanzania (TANGA) were tested for insecticide resistance. Initially, the resistance ratio (RR) to chlorpyrifos was 41.8, to temephos 30.8, to propoxur 3.7. After 2–3 years of laboratory culture, resistance to chlorpyrifos and propoxur had declined (chlorpyrifos 5.7, 3.8; propoxur 1.9, permethrin 1.9). Significant synergism was found between s, s, s-tributyl trithiophosphate (DEF) and chlorphyrifos, reducing the RR from 8.0 to 2.5. Synergism between piperonyl butoxide and permethrin was less than in a susceptible control strain. Twelve esterase isozymes of different relative mobilities (Rm) on polyacrylamide gel electrophoresis were identified, ten of which remained when the strain was reinvestigated two years (approximately 32 generations) later. Null activity for all but one of these bands was observed in some larvae. Four esterase bands (Rm 0.25, 0.27, 0.31, 0.34, designated A2, A3, B2, B3) showed polymorphism in activity, with very intense bands in some larvae. The mean frequency of bands with activity greater than standard, declined as organophosphorus (OP) resistance declined, but resistance was unconnected with the frequency of nulls at these positions. In mass larval assays of in vitro sensitivity of acetylcholinesterase (AChE) to propoxur, the I50 exceeded 10x10−4M, compared with 0.1x10−4M in a reverted resistant strain (RANGOON). Single larvel assays revealed heterogeneity, which was interpreted on the basis of an AChE resistance allele (AceR) with a frequency of 0.23.

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