• Korean journal of applied entomology
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• v.30 no.2
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• pp.117-123
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• 1991

Acetylcholinesterase(AChE) and esterase activities as mechanisms of resistance to fenobucarb, carbofuran and diazinon in the insecticide-selected brown planthopper strains were investigated. Although there was no significant difference in AChE activity from suscept tible and resistant strains, AChE insensitivity was highly increased in the carbam없e insecticide-selected strains. On the other hand, esterase activity was moderately increa잃d in all the s selected strains. It is concluded that the cross-resistance and the level of resistance in the b brown planthopper can be explained by the combination of altered AChE and high esterase a activity, although a possible involvement of other factor(s) can not be excluded.

• Journal of Applied Biological Chemistry
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• v.51 no.3
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• pp.95-101
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• 2008

The gene encoding a putative esterase of Xanthomonas oryzae pv. oryzae was cloned using PCR technique. The gene was expressed with His6 tag in E. coli. One-step purification of the recombinant esterase with Ni-NTA resin resulted in one band by SDS-PAGE analysis. The purified enzyme showed a molecular weight of 30 kDa, as expected, therefore the enzyme was a mononer. The enzyme was the most active toward p-nitrophenyl (p-NP) acetate and p-NP-butyrate to a lesser extent. However, the enzyme could not hydrolyze p-NP-myristate, palmitate, and stearate. Therefore, the enzyme is considered as an esterase, very different from lipase. The purified esterase had optimal pH at around 8.0 and was stable in a broad range of pH values. The optimal temperature ranged from 30 to $40^{\circ}C$, and the residual activity observed after heat treatment at $55^{\circ}C$ for 20 min was 72 % of the initial activity. The activity was inhibited by the presence of copper and cobalt ions.

• Biotechnology and Bioprocess Engineering:BBE
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• v.6 no.3
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• pp.179-182
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• 2001

Porcine liver esterase was immobilized in polyacrylamide gel for the enantioselective production of levofloxacin from ofloxacin butyl ester. The initial activity of immobilized esterase was found to be significantly affected by the polyacrylamide gel composition. The optimum concentrations of monomer and crosslinker were determined to be 20% and 8.3%, respectively. The activity of immobilized esterase was 55.4% compared to a free enzyme. Enantiomeric excess was maintained at 60%, almost the same level as that of free enzyme. In addition, the immobilized esterase could be used repeatedly up to 10 times without experiencing any severe loss of activity and enantioselectivity.

• Journal of Microbiology and Biotechnology
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• v.16 no.1
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• pp.145-148
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• 2006

A new functional lipolytic enzyme (AT4) has recently been found from Agrobacterium tumefaciens C58 Cereon using a genome-wide approach. The enzyme has some sequence similarity to E. coli acetyl hydrolase, Emericella nidulans lipase, Moraxella sp. lipase, Acinetobacter lwoffii esterase, and Streptomyces hygroscopicus acetyl hydrolase. However, the sequence similarities are very low (less than $25\%$), suggesting that it is a new lipase/esterase enzyme. ill the present study, intact cell of the A. tumefaciens strain was shown to have lipolytic activity on a tributyrin-LB plate. The AT4 gene was then expressed at a high level in E. coli BL21 (DE3) cells and the enzyme was purified simply by Ni-NTA column chromatography. The purified enzyme showed hydrolytic activity toward p-nitrophenyl caproate, but not toward olive oil, suggesting that the AT4 enzyme was a typical esterase rather than lipase. AT4 esterase had a maximum hydrolytic activity at $45^{\circ}C$ and pH 8.0, when p-nitrophenyl caproate was used as a substrate. It was relatively stable up to $40^{\circ}C$ and at pH 5.0-9.0. Calcium ion and EDT A did not affect the activity and thermal stability of the enzyme. As for substrate specificity, AT4 enzyme could rapidly hydrolyze acetyl and butyl groups from p-nitrophenyl esters and 1-naphthyl esters. In addition, it also released acetyl residues from acetylated glucose and xylose substrates. Therefore, this new esterase enzyme might be used as a biocatalyst in acetylation and deacetylation reactions performed in the fine chemical industry.

• Korean journal of applied entomology
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• v.32 no.3
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• pp.265-270
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• 1993

The German cockroach(Blattelia germanica) population~ were successIVely selected with ch\orpyrifos and permethrin during the six generations. The resulting resistant $R_{chtorpenfos}$(Rc) and $R_{permethnn}$(Rp) stra.ins were studied to investigate the esterase activity by spectrophotometer, filter parper test, and electrophoresis. Esterase-$\alpha$ activities by filter paper test showed 2.65 and LBZ times higher in the Rc and Rp strains than the susceptible strain, respectively. ln the spectrophoLometer method, the esterase activit18s to $\alpha$-and $\beta$-naphthyl acetate were increased 2.34 and 5.28 times in the Rc than susceptible strain, and 1.48 and 2.92 times in the Rp Limn susceptible stram, respectlvely. Zymogram patterns of eslerase isozyme by agarose gel electrophoresis showed totally five bands. The Rc and Rp strains showed two additive bands as, Est-2 and Est-3, which were not shown in the susceptible strain. but the Rp strain dId not show Est-5 bands which was COlumon in the Rc and susceptible strams.

• International Journal of Industrial Entomology and Biomaterials
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• v.9 no.1
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• pp.59-63
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• 2004

By using PAGE, a study was made on the nonspecific esterase spectra of female genital organs and eggs in Bombyx mori L. The expression of 11 esterase bands was detected during ontogenesis of races and inter-races hybrids kept in Bulgaria. The gene activity of 9 esterase loci was assumed. Esterases specific for the spectrum of diapausing eggs were observed. In two esterase zones, intra- and inter-breed polymorphism was found. Based on the same breed specific expression, the existence of correspondence between esterase bands from spectra of different silkworm tissues and organs was suggested. Stage-specific expression of esterases in female genital glands, indicative of differentiated gene activity during ontogenesis, was established.

• Journal of the Korean Graphic Arts Communication Society
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• v.26 no.1
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• pp.17-28
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• 2008

The wood-pulp is treated with the three enzymes; Endo-xylanase, exo-xylanase and acetyl-esterase. The maximum value of relative activity appeared 0.95 in acetyl-esterase at $40^{\circ}C$, 0.9 in exo-xylanase at $40^{\circ}C$, and 0.8 in endo-xylanase at $50^{\circ}C$, respectively. And it has measured 0.8 in endo-xylanase, 0.95 in acetyl-esterase at pH 6 and 0.9 in exo-xylanase at pH 5, while the maximum value of relative activity does not rely on reaction time for three enzymes treatment, and the value was about 0.9, respectively. We have watched that decreased Kappa number and increased brightness. And it turned out that the three enzyme produced a lot of reducing sugar with wood-pulp treatment.

• Journal of Microbiology and Biotechnology
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• v.30 no.2
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• pp.216-225
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• 2020

An esterase gene, estA1, was cloned from Alteromonas sp. 39-G1 isolated from the Beaufort Sea. The gene is composed of 1,140 nucleotides and codes for a 41,190 Da protein containing 379 amino acids. As a result of a BLAST search, the protein sequence of esterase EstA1 was found to be identical to Alteromonas sp. esterase (GenBank: PHS53692). As far as we know, no research on this enzyme has yet been conducted. Phylogenetic analysis showed that esterase EstA1 was a member of the bacterial lipolytic enzyme family IV (hormone sensitive lipases). Two deletion mutants (Δ20 and Δ54) of the esterase EstA1 were produced in Escherichia coli BL21 (DE3) cells with part of the N-terminal of the protein removed and His-tag attached to the C-terminal. These enzymes exhibited the highest activity toward p-nitrophenyl (pNP) acetate (C₂) and had little or no activity towards pNP-esters with acyl chains longer than C₆. Their optimum temperature and pH of the catalytic activity were 45℃ and pH 8.0, respectively. As the NaCl concentration increased, their enzyme activities continued to increase and the highest enzyme activities were measured in 5 M NaCl. These enzymes were found to be stable for up to 8 h in the concentration of 3-5 M NaCl. Moreover, they have been found to be stable for various metal ions, detergents and organic solvents. These salt-tolerant and chemical-resistant properties suggest that the enzyme esterase EstA1 is both academically and industrially useful.

• Microbiology and Biotechnology Letters
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• v.22 no.5
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• pp.507-514
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• 1994

Acetyl xylan esterase was produced by E. coli HB101 harboring a recombinant plasmid pKMG6 which contained the estI gene of Bacillus stearothermophilus. The maximum production was observed when the E. coli strain was grown at 37$\circC for 12 hours in the medium containing 0.5% acetyl xylan, 1.0% tryptons, 1.0% sodium chloride, and 0.5% yeast extract. The esterase produced was purified to homogeneity using a combination of ammonium sulfate fractionation, DEAE Sepharose CL-6B ion exchange chromatography and Sephacryl S-200 gel filtration. The native enzyme had an apparent molecular mass of 60 kd and was composed of two identical subunits of 29 kd. The N-terminal amino acid sequence of the polypeptide was Ala-X-Leu-Gln- Ile-Gln-Phe-X-X-Gln. The acetyl esterase displayed a pH optimum of 6.5 and a temperature opti- mum of 45$\circC. The heavy metal ions such as Ag$^{++}$, Hg$^{++}$ and Cu$^{++}$ inhibited nearly completely the activity of the esterase, and no specific metal ion was found to be required for the enzyme activity. The enzyme readily cleaved MAS, $\beta$-D-glucose pentaacetate, $\alpha$-naphthyl acetate, $\rho$-nitrophenyl acetate as well as acetyl xylan, but had no activity on $\rho$-nitrophenyl propionate, $\beta$-nitrophenyl butyrate or $\beta$-nitrophenyl valerate. The Km and Vmax values for MAS were 2.87 mM and 11.55 $\mu$mole/min, respectively. Synergistic behavior was demonstrated with a combination of xylanase and esterase from B. stearothermophilus in hydrolyzing acetyl xylan.

• The Korean Journal of Pesticide Science
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• v.8 no.1
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• pp.16-21
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• 2004

A series of experiments was conducted to determine the toxicities of thiodicarb on the six lepidopterous pests (Pseudaletia separata, Plutella xylostella, Palpita indica, Spodoptera exigua, Helicoverpa assulta, Spodoptera litura) and to elucidate factors insecticidal effects mechanism of thiodicarb. Thiodicarb was very effective against six lepidopterous young larvae, but less effective to the old larvae and it acted slowly. Thiodicarb inhibited acetylcholinesterase and glutathione S-transferase activities, but not inhibit esterase activity.