Variation In Esterase Activity Research Articles

Variation in Esterase Activity Among Different Aedes aegypti L. Populations from the Dooars and Terai Regions of West Bengal, India

Mosquitoes are responsible for transmitting the most important vector-borne diseases like malaria, dengue etc. across the world, especially in tropical countries. The most prominent species of the genus Aedes, A. aegypti and A. albopictus act as vectors for numerous viral infections. Because of non-availability of vaccine for dengue fever, vector control stands the only approach to prevent the viral transmission. As per recommendations by World Health Organization (2015), the main insecticides used for mosquito control are DDT, malathion, chlorpyrifos, temephos, bendiocarb and synthetic pyrethroids. Excessive and unwanted usage of insecticides not only increases vectors’ resistance to insecticides, but also results in cross resistance to other insecticides. In mosquitoes, metabolic detoxifications of insecticides by detoxifying enzymes are the main strategy to withstand recurrent exposure to synthetic insecticides. Esterases are one of the three gene families of detoxification enzymes involved in metabolic detoxification of insecticide and confers resistance for organophosphorus insecticide (OP) as well as for carbamate insecticide. In the present study, the activity of α- and β-esterases have been evaluated in different A. aegypti populations collected from the Dooars and Terai regions of West Bengal, India. The activity of α-esterases was 1.2–3.1 fold and β-esterases was 2.0–23.0 fold higher than laboratory control population. The electro-phoregrams of α-esterases showed expression of 11 isozymes from two gene loci and for β-esterases showed expression of 09 isozymes from two gene loci in all the field populations of A. aegypti. The results showed a significant variation of esterase activity and isozyme expression among different population indicating variability in biochemical susceptibility among the populations. The present work presents first hand data on biochemical resistance of A. aegypti in this region and may be used as an integral component for planning and evaluation of vector-borne diseases and integrated vector management programmes.

Genetic Characterization of Esterase Activity Variants Associated with an Esterase Gene Amplification in a Strain of Culex pipiens from California.

In the Culex pipiens complex, a common mechanism of insecticide resistance is amplification of esterase genes leading to overproduction of detoxifying esterase enzymes. A number of electrophoretic esterase alleles have been identified, and in field populations individuals with the same esterase electromorph can exhibit a wide range of esterase enzyme activities. We isolated and characterized esterase activity variants associated with the esterase B1 electromorph from a field strain. A mating scheme was used to isolate chromosomes with esterase genes from the strain into 45 families. Twenty-six of the families received esterase genes from the field strain that conferred elevated esterase activity. Mean esterase activities in these families ranged from 43 to 695nmoles α-naphthyl acetate hydrolyzed/min/mg protein. Variance components indicated that genetic variance (i.e., genetic differences among families) accounted for 77% of the total variation in esterase activity. A comparison of mean esterase activities indicated that there were at least 11 different esterase activity variants contributing to the observed genetic variation in esterase activity among the 26 families. The relevance of these results to understanding the dynamics of amplified esterase genes in populations is discussed.

Hydroxycinnamic Acid Ethyl Esters as Precursors to Ethylphenols in Wine

A method for determining ethyl coumarate and ethyl ferulate in wine using GC-MS with deuterium-labeled analogues has been developed and used to measure the evolution of these two esters during the production of two commercial monovarietal red wines, cv. Grenache and Shiraz. During fermentation, the concentration of ethyl coumarate rose from low levels to 0.4 mg/L in Grenache and 1.6 mg/L in Shiraz wines. These concentrations then increased further during barrel aging to 1.4 and 3.6 mg/L, respectively. The concentration of ethyl ferulate was much lower, reaching a maximum of only 0.09 mg/L. Conversion of ethyl coumarate and ethyl ferulate to their corresponding ethylphenols was observed during fermentations of a synthetic medium with two strains of Dekkera bruxellensis (AWRI 1499 and AWRI 1608), while a third (strain AWRI 1613) produced no ethylphenols at all from these precursors. Strains AWRI 1499 and 1608 produced 4-ethylphenol from ethyl coumarate in 68% and 57% yields, respectively. The corresponding yields of 4-ethylguaiacol from ethyl ferulate were much lower, 7% and 3%. Monitoring of ethyl coumarate and ethyl ferulate concentration during the Dekkera fermentations showed that the selectivity for ethylphenol production according to yeast strain and the precursor was principally a result of variation in esterase activity. Consequently, ethyl coumarate can be considered to be a significant precursor to 4-ethylphenol in wines affected by these two strains of Brettanomyces/Dekkera yeast, while ethyl ferulate is not an important precursor to 4-ethylguaiacol.

Effect of dihydrodillapiole on pyrethroid resistance associated esterase inhibition in an Indian population of Spodoptera litura (Fabricius)

Resistance in Spodoptera litura (Fabricius) has been attributed to enhanced detoxification of insecticides by increased levels of esterases, oxidases and/or glutathione S-transferases. Enzyme inhibiting insecticide synergists can be employed to counter increased levels of such enzymes in S. litura. Dihydrodillapiole induced synergism of pyrethroid toxicity was examined in the laboratory-reared third instar larval population of S. litura collected in Delhi (susceptible), and Guntur (resistant) region of Andhra Pradesh, India. The Guntur population was found to be 7.04 and 10.19 times resistant to cypermethrin and lambdacyhalothrin, respectively. The activity of cypermethrin, lambdacyhalothrin and profenophos against susceptible and resistance populations of S. litura, was gradually increased when used along with a plant-derived insecticide synergist dihydrodillapiole. The α-naphthyl acetate hydrolysable esterase activity in Delhi population was less as compared to the Guntur population. Resistance associated esterases in Delhi population were inhibited by pre-treatment with dihydrodillapiole. The esterase level in insect was instantly reduced initially, sustained for about 3 h and equilibrated at 4 h post treatment. The esterase activity of Guntur population was increased to 1.28 μmoles/mg/min at 2 h post treatment and subsequently reduced to lower than 0.70 μmoles at 4–12 h post treatment. The variation in esterase activity is suggestive of its homeostatic regulation in test populations. Dihydrodillapiole thus caused significant reduction of resistance in S. litura to cypermethrin, lambda cyhalothrin and profenophos.

The hydrolytic activity of esterases in the yeastSaccharomyces cerevisiaeis strain dependent

Ester precursors of fluorogenic or chromogenic probes are often employed in studies of yeast cell biology. This study was aimed at a comparison of the ability of several commonly used laboratory wild-type Saccharomyces cerevisiae strains to hydrolyse the following model esters: fluorescein diacetate, 2-naphthyl acetate, PNPA (p-nitrophenyl acetate) and AMQI (7-acetoxy-1-methylquinolinum iodide). In all the strains, the esterase activity was localized mainly to the cytosol. Considerable differences in esterase activity were observed between various wild-type laboratory yeast strains. The phase of growth also contributed to the variation in esterase activity of the yeast. This diversity implies the need for caution in using intracellularly hydrolysed probes for a comparison of yeast strains with various genetic backgrounds.

Enzymatic activity in the activated-sludge floc matrix.

The enzymatic activity of activated sludge was investigated with special emphasis on the localization of the enzymes in the sludge floc matrix. Activated sludge from an advanced activated-sludge treatment plant, performing biological N and P removal, was used. An enzymatic fingerprint was established using a panel of six different enzymes. The fingerprint revealed peptidase as the most dominating specific enzyme tested. By monitoring sludge bulk enzymatic activity over a 3-month period using fluorescein diacetate as an enzyme substrate, considerable variations in activity were observed even over short periods (a few days). The variation in esterase activity was to some extent correlated to the presence of humic compounds in the sludge, but not to the sludge protein content. Comparison of full sludge enzyme activity to the activity of a batch-grown sludge culture indicated that enzymes accumulated in sludge flocs. A large proportion of the exoenzymes were immobilized in the sludge by adsorption in the extracellular polymeric substances (EPS) matrix. This was demonstrated by extraction of EPS from the activated sludge using cation exchange. Contemporary to the release of EPS a very large fraction of the exoenzymes was released into the water. This showed that the exoenzymes should be considered to be an integrated part of the EPS matrix rather than as direct indicators of the microbial activity or biomass.

Quantitative genetic variation of esterase activity associated with a gene amplification in Culex quinquefasciatus

Amplification of the esterase B1 gene is responsible for insecticide resistance in the mosquito Culex quinquefasciatus. We used a mating scheme to isolate chromosomes carrying amplified esterase genes from a long-selected laboratory strain (Tem-R) to determine whether observed variation in esterase activity had a genetic basis. The amplified esterase genes segregated as a block and a possible newly arisen esterase B1 copy-number variant was found among the progeny of females which carried amplified B1 genes on only one homologue. A quantitative genetic analysis found significant genetic variation of esterase activity among families which carried different amplification-bearing chromosomes from the Tem-R strain. Esterase B1 copy-number variation among these Tem-R chromosomes is the most likely basis for the observed genetic variation in esterase activity.

Genetic variation in response of the gypsy moth to aspen phenolic glycosides

We investigated genetic variation in response of a wild strain of gypsy moths, Lymantria dispar, to phenolic glycosides isolated from Populus. For 12 families, first instar survival varied little among family groups fed a control artificial diet, but LT 50 values differed significantly among groups fed an artificial diet containing phenolic glycosides. First instar survival rates were positively correlated with esterase enzyme activity. Relative growth rates of fourth instars were influenced by diet and by family. A nearly significant dietXfamily interaction term indicates that family (genotype) influences gypsy moth response to phenolic glycosides. Prior consumption of phenolic glycosides induced esterase activity in fifth instars. Esterase activity was influenced by diet, family and dietXfamily interaction. Genetic variation in esterase activity may explain variation in larval response to phenolic glycosides.