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At least 1,225 records · Page 68Linked to original sources
PubMed1994

Cloning and expression of Pseudomonas putida esterase gene in Escherichia coli and its use in enzymatic production of D-beta-acetylthioisobutyric acid.

The esterase catalyzes the stereoselective hydrolysis of methyl DL-beta-acetylthioisobutyrate (DL-ester) to give D-beta-acetylthioisobutyric acid (DAT). To use the enzyme for DAT production, the esterase gene of Pseudomonas putida was cloned and expressed in E. coli. The recombinant E. coli containing the esterase gene produced a large amount of the enzyme in an active form. This strain could be used for the asymmetric synthesis of DAT.

Bacterial Proteins↗
PubMed2004

Thermostable esterase from a thermoacidophilic archaeon: purification and characterization for enzymatic resolution of a chiral compound.

Homolog to lipolytic enzymes having the consensus sequence Gly-X-Ser-X-Gly, from the Sulfolobus solfataricus P2 genome, were identified by multiple sequence alignments. Among three potential candidate sequences, one (Est3), which displayed higher activity than the other enzymes on the indicate plates, was characterized. The gene (est 3) was expressed in Escherichia coli, and the recombinant protein (Est3) was purified by chromatographic separation. The enzyme is a trimeric protein and has a molecular weight of 32 kDa in monomer form in its native structure. The optimal pH and temperature of the esterase were 7.4 and 80 degrees C respectively. The enzyme showed broad substrate specificities toward various p-nitrophenyl esters ranging from C2 to C16. The catalytic activity of the Est3 esterase was strongly inhibited by phenylmethylsulfonyl fluoride (PMSF) and diethyl p-nitrophenyl phosphate. Based on substrate specificity and the action of inhibitors, the Est3 enzyme was estimated to be a carboxylesterase (EC 3.1.1.1). The enzyme with methyl (+/-)-2-(3-benzoylphenyl)propionate-hydrolyzing activity to (-)-2-(3-benzoylphenyl)propionic acid displayed a moderate degree of enantioselectivity. The product, (-)-2-(3-benzoylphenyl)propionic acid, rather than its methyl ester, was obtained in 80% enantiomeric excess (e.e.(p)) at 20% conversion at 60 degrees C after a 32-h reaction. This result indicates that S. solfataricus esterase can be used for application in the synthesis of chiral compounds.

Amino Acid Sequence↗
PubMed1978

Kinetic investigations of liver microsomal esterases with oxazepam esters.

Hepatic microsomal esterases of the mouse responsible for the bioactivation of inactive (prodrug) esters of the centrally acting oxazepam were studied. The enzymes are situated on the cytoplasmic side of the microsomes. The esterases are partly solubilized and partly inactivated by homogenization in aqueous glycerol and treatment with deoxycholate. There is good correlation between the rates of hydrolysis and steric constants of the acyl moiety. Substrate binding increases to an optimum with the number of carbon atoms in the acyl moiety and is of hydrophobic nature. An attempt has been made to classify the esterases on the basis of the effect of inhibitors and activators.

Animals↗
PubMed2005

Loss of Swiss cheese/neuropathy target esterase activity causes disruption of phosphatidylcholine homeostasis and neuronal and glial death in adult Drosophila.

The Drosophila Swiss cheese (sws) mutant is characterized by progressive degeneration of the adult nervous system, glial hyperwrapping, and neuronal apoptosis. The Swiss cheese protein (SWS) shares 39% sequence identity with human neuropathy target esterase (NTE), and a brain-specific deletion of SWS/NTE in mice causes a similar pattern of progressive neuronal degeneration. NTE reacts with organophosphate compounds that cause a paralyzing axonal degeneration in humans and has been shown to degrade endoplasmic reticulum-associated phosphatidylcholine (PtdCho) in cultured mammalian cells. However, its function within the nervous system has remained unknown. Here, we show that both the fly and mouse SWS proteins can rescue the defects that arise in sws mutant flies, whereas a point mutation in the proposed active site cannot restore SWS function. Overexpression of catalytically active SWS caused formation of abnormal intracellular membraneous structures and cell death. Cell-specific expression revealed that not only neurons but also glia depend autonomously on SWS. In wild-type flies, endogenous SWS was detected by immmunohistochemistry in the endoplasmic reticulum (the primary site of PtdCho processing) of neurons and in some glia. sws mutant flies lacked NTE-like esterase activity and had increased levels of PtdCho. Conversely, overexpression of SWS resulted in increased esterase activity and reduced PtdCho. We conclude that SWS is essential for membrane lipid homeostasis and cell survival in both neurons and glia of the adult Drosophila brain and that NTE may play an analogous role in vertebrates.

Animals↗
PubMed1987

Postnatal differentiation and endocrine control of esterase isoenzymes in the mouse epididymis.

At 2 weeks of age, 11 isoenzymes were expressed and similar banding patterns on vertical polyacrylamide gel electrophoresis (PAGE), stained by alpha- or beta-naphthyl acetate as a substrate, were obtained for tissues or fluids from the proximal and the distal parts of the mouse epididymis. After this period, the emergence of new bands or the disappearance of certain others led to a regional differentiation which appeared progressively in tissues and fluids, earlier in the distal part than in the proximal part. The changes occurring during epididymal differentiation affected the isoenzymes specific to the epididymis more than those common to testis and serum. Castration of adult mice induced a decrease in esterase activity and changes in the number of isoenzymes, leading to the loss of regional specificity of the banding patterns. The dedifferentiation process modified the electrophoretic profiles of the distal part only. Androgen replacement restored the regional specificity of cytosol banding patterns after 2 weeks of treatment and the normal intensity of bands after 4 weeks. Some differences in the fluid isoenzymes nevertheless persisted. The androgen-dependence of esterase isoenzymes can be attributed to circulatory hormones rather than to androgens from the testis via the rete testis as shown by efferent ductule ligation which did not modify the epididymal esterase profiles.

Androgens↗
PubMed2002

African dung beetle Onthophagus gazella Fabricius (Coleoptera: Scarabaeidae) esterase isozymes.

African beetles Onthophagus gazella from both sexes were analyzed by electrophoresis for an investigation of esterase isozymes using alpha-naphthyl propionate and methylumbelliferyl propionate as substrates. Only one of the esterases (Est. 6) reacted with one of the substrates (alpha-naphthyl propionate). Six areas of activity were found, two of them being polymorphic (Est. 3 and Est. 4). For presence of Est. 3, 337 individuals were analyzed, including descendants of 32 controlled crossings: two alleles were identified, whose frequencies are Est. 3A = 0.447 and Est. 3B = 0.553. The population is in equilibrium for this locus (qui-square = 4.18; 0.2 > P > 0.1). For Est. 4, 338 individuals, descendants of 32 controlled crossings, were analysed. In this case, three alleles were identified whose frequencies are: Est. 4A = 0.277; Est. 4B = 0.661; and Est. 4C = 0.062. The population is not in equilibrium for this locus (qui-square = 40.259; p < 0.001). Two esterases were detected only in the pupal stage and another one in larvae. Of the 23 loci analyzed in these insects up to now, 3 are polymorphic (13%), which indicates very low variability in the population here studied.

Animals↗
PubMed2002

Isolation and identification of an esterase from a Mexican strain of Boophilus microplus (Acari: Ixodidae).

A strain of Mexican Boophilus microplus (Cz) collected near Coatzacoalcos, Veracruz, Mexico, exhibits a moderate, but significant, level of permethrin resistance. Unlike other highly permethrin resistant strains, the Cz strain does not have a mutation within the sodium channel gene that results in target-site insensitivity. However, the Cz strain possesses a substantial increase in general and permethrin esterase activity relative to highly permethrin resistant and control strains suggesting the involvement of a metabolic esterase(s) in the expression of permethrin resistance. We report the isolation of a 62.8 kDa protein from Cz strain larvae that we think is the esterase previously reported as Cz EST9. In addition, internal amino acid sequence data obtained from the 62.8 kDa protein suggest that it is the gene product of a previously reported B. microplus carboxylesterase cDNA. We propose that the 62.8 kDa protein (Cz EST9) has permethrin hydrolytic activity and as a result plays an important role in Cz strain resistance to permethrin.

Amino Acid Sequence↗
PubMed2005

Roles played by esterase activity and by a sodium channel mutation involved in pyrethroid resistance in populations of Boophilus microplus (Acari: Ixodidae) collected from Yucatan, Mexico.

Pyrethroid resistance in Boophilus microplus (Canestrini) (Acari: Ixodidae) was studied by correlating discriminating-dose (DD) bioassay results and esterase activity or the frequency of a sodium channel mutation known to be involved in pyrethroid resistance in nine field strains of B. microplus from Yucatan, Mexico. Two tick strains (P67 and B74) were identified as susceptible to cypermethrin, deltamethrin, and flumethrin by DD, one strain (P65) was susceptible to cypermethrin and resistant to deltamethrin and flumethrin, and six strains were resistant to cypermethrin, delta-methrin, and flumethrin (T11, M10, C54, R49, B71, and T66). By using polymerase chain reaction, only 6.0 and 6.2% of resistance allele (R) was found in the susceptible strains (P67 and B74, respectively). In the T66 strain, with 100% of larval survival to the DD of pyrethroids as measured by the larval packet test (LPT), 98.0% of the gene pool contained the R allele. Positive correlations between the larval survival and the percentage of the R allele were found (deltamethrin r2 = 0.8875, P < 0.01; cypermethrin r2 = 0.8563, P < 0.01; and flumethrin r2 = 0.8491, P < 0.01). There were no significant correlations between the level of larval survival and esterase-based hydrolytic activity. It was concluded that within the B. microplus populations studied, resistance to flumethrin, deltamethrin, or cypermethrin was because of the novel sodium channel mutation (Phe-->Ile amino acid substitution in the S6 transmembrane segment of domain III), and there was a correlation between tick mortality by pyrethroid exposure (larval survival) and the presence of R allele. It was not determined whether enhanced esterase-based hydrolytic activity was involved in pyrethroid resistance in the populations tested.

Animals↗
PubMed2001

Overproduced esterases in Culex pipiens quinquefasciatus (Diptera: Culicidae) from Vietnam.

The electrophoretic polymorphism of loci encoding for 10 enzymes was studied in Culex p. quinquefasciatus Say from six localities of Vietnam. The analysis of 11 "neutral genes" showed that differentiation among samples was low, but significant (Fst = 0.06), and significantly related to geographic distance between sample sites. These results are similar to those observed in other countries (Europe and west Africa). A single type of overproduced esterases (A2-B2) was observed, and its frequency was high (60-100%) in all samples. This situation is in sharp contrast with that observed in other countries of South East Asia (China, South Korea and Japan), where two or more types of overproduced esterases have been reported. A map summarizing the geographic distribution of Asian Cr. p. quinquefasciatus with overproduced esterases is provided.

Animals↗
PubMed1975

Effects of ovarian steroid hormones on esterases in the rat endometrium.

A technique in which uterine luminal epithelium is separated from the remainder of the endometrium by rapidly vibrating everted uterine cornua in a 3-5 mM solution of EDTA has been developed. Examination of the hormonal sensitivities and physiological roles of the tissue components of the endometrium is thus facilitated. Biochemical and histochemical studies of epithelial, stromal and endometrial esterases have shown that the rate of hydrolysis of alpha-naphthyl acetate is significantly higher in epithelial and endometrial tissue extracts during pro-oestrus than at any other stage of the oestrous cycle. In ovariectomized animals, oestradiol-17 beta caused a 60% increase in the rate of esterase activity over that of control animals, whereas medroxyprogesterone acetate had no effect. These findings suggest that the variations in the levels of neutral lipids in the uterine luminal epithelium of non-pregnant mature female rats result from the periodic stimulation of the epithelial esterases by the cyclically increased levels of plasma oestrogens.

Animals↗
PubMed1988

Use of a leukocyte esterase dipstick to detect Chlamydia trachomatis and Neisseria gonorrhoeae urethritis in asymptomatic adolescent male detainees.

We tested 91 asymptomatic adolescent male detainees in a short-stay detention facility in Seattle, Washington for the presence of leukocyte esterase in first-catch urine and for Chlamydia trachomatis and Neisseria gonorrhoeae infection. C. trachomatis was isolated from 10 subjects (11 per cent) and N. gonorrhoeae from five (5 per cent). Dipsticks detected leukocyte esterase in the urine of all 15 subjects with either infection and of 13 subjects with neither infection. Detection of leukocyte esterase was 100 per cent sensitive, 83 per cent specific, and 54 per cent predictive for the presence of either organism.

Adolescent↗
PubMed1992

Ester hydrolysis and conjugation reactions in intact skin and skin homogenate, and by liver esterase of rabbits.

1. Procaine, 2-chloroprocaine, ethyl aminobenzoate and methyl salicylate were added at various concentrations to liver esterase, supernatant of skin homogenate, or single-pass perfused ears of rabbits. 2. Vmax of product formation by purified liver esterase correlated with the rank order of the distribution coefficients (n-octanol/buffer) of the substrates and ranged between 11 and 1100 pmol/min per micrograms protein. Km values were between 20 and 50 microM. 3. No correlation was observed when the apparent enzyme kinetics, calculated by non-linear adaptation, were compared with each other after substrate administration to skin, arterial influx, or incubation with skin homogenate. 4. An acid labile conjugate of ethyl 4-aminobenzoate was found, mainly during arterial perfusion and in supernatant of skin homogenate, after administration of ethyl 4-aminobenzoate. 5. Acetamidobenzoic acid was observed in quantities of about 10% of the free 4-aminobenzoic acid during dermal or arterial application of procaine. This metabolite was not found with ethyl 4-aminobenzoate. 6. The results from isolated rabbit ear perfusion differ quantitatively and qualitatively with those obtained from supernatant of skin homogenate or purified liver esterase.

Anesthetics, Local↗
PubMed1985

Esterase activity, exclusion of propidium iodide, and proliferation in tumor cells exposed to anticancer agents: phenomena relevant to chemosensitivity determinations.

Cellular esterase activity and the ability to exclude propidium iodide were examined after exposing tumor cells to anticancer agents. In general, esterase activity and the ability to exclude propidium iodide continued when cells proliferated and disappeared when proliferation was inhibited. However, with a number of preparations, drug exposure inhibited proliferation while esterase activity and propidium iodide exclusion persisted. These indications of persisting cell function or viability after drug exposure may be relevant to a potential for tumor cell recovery. When the viability of established cell lines progressively declined on days 4 and 7 following drug exposure, recovery did not occur. When proliferative recoveries occurred, viabilities remained elevated. Estimates of in vitro sensitivity by proliferation-related criteria were contrasted by persistent high viability estimates in 22% of the determinations performed with primary tumor cell preparations. The potential for recovery may explain the disappointing ability of proliferative chemosensitivity assays to predict clinical sensitivity.

Antineoplastic Agents↗
PubMed1993

cDNA sequence, gene structure, and cholinesterase-like domains of an esterase from Caenorhabditis elegans mapped to chromosome V.

The structure of an esterase gene from Caenorhabditis elegans has been determined by comparison of the sequences in genomic and cDNA clones. The gene was mapped close to the center of chromosome V (1.7 centimorgans to the left of dpy-11) and is therefore distinct from the gut esterase gene ges-1. It possessed 7 short introns. The 5' splice site of intron 3 presented the sequence GC instead of the usual GT that was found in the other six introns. The cDNA was trans-spliced with the short leader SL1. The open reading frame indicated that a protein of 557 aminoacids was encoded. The deduced aminoacid sequence did not present a signal peptide at the N-terminal but a potential N-myristoylation site (GXXXS) provided that the initiator methionine was removed. This protein should therefore remain intracellular. Comparison of this C. elegans sequence to other protein sequences in databases, as well as the analysis of the secondary structure in the protein showed that it belongs to the subgroup of esterases in the alpha/beta hydrolase fold family.

Amino Acid Sequence↗
PubMed1975

Pregastric esterase in milk sham fed to adult jersey steers.

Pregastric esterase activity was detected in reconstituted nonfat milk sham fed from a nipple pail to two 4-yr-old rumen-fistualted steers. Lipolytic activity, determined in a medium containing 5% tri-n-butyrin, averaged 8.6 plus or minus .4 lipase units. Further assays, in which activitiy was measured by free fatty acids released from a condensed milk substrate, averaged 166.9 plus or minus 9.2 mumol. These values are higher than those noted for young calves, indicating that secretion of pregastric esterase may persist in cattle beyond calfhood. Esterase activity in one of the steers fed whole milk until he was 2 yr of age showed no marked residual effect of earlier intake of milk fat.

Age Factors↗
PubMed1980

Effects of pregastric esterase on utilization of whole milk by preruminant calves.

The role of pregastric esterase was investigated in four abomasally-cannulated calves during a sequence of ten 3-day periods beginning when calves were 2 to 5 days of age. Two calves were fed whole milk from nipple bottles to maximize exposure to pregastric esterases, and two other calves were given milk by infusion directly into the abomasum to minimize exposure. The initial system of feeding each calf was continued for eight periods after which treatments were reversed. Postfeeding lipolytic activity of samples of abomasal contents and of intragastric lipolysis of milk fat were markedly greater for orally-fed calves than for abomasally-fed. Systems of feeding effected no significant differences in a) digestibility of dry matter, fat, crude protein, and nitrogen-free extract, b) retention of nitrogen, and c) percentage weight gains. Digestibility of dry matter, crude protein, and nitrogen-free extract of milk and retention of nitrogen were greater in later periods than in initial. Although age of calves was a positive factor associated with utilization of milk, decreased exposure of milk to pregastric esterase and the resulting reduction of lipolysis in the abomasum did not effect a detectable lowering of milk utilization by calves in age groups studied.

Abomasum↗
PubMed1987

Biological effects of acetomycin. II. Inactivation by esterases in vitro.

Acetomycin has antitumor activity in vitro but not in vivo. HCT-8 human colon adenocarcinoma assays in the presence of a drug metabolizing system (rat liver S9 fraction) demonstrated that liver enzymes inactivated acetomycin. The structure of acetomycin suggested that an esterase could be the key inactivating enzyme. Assays with porcine liver esterase (EC 3.1.1.1) showed that this enzyme rapidly abolishes the activity of acetomycin against HCT-8 cells. The potential utility of acetomycin as an antitumor agent thus depends on finding a means of preventing esterase inactivation.

Adenocarcinoma↗
PubMed1976

[Heterogeneity and heat resistance of esterases of the pancreas and liver of rats].

A higher heat resistance of loosely-attached microsomal esterases as compared with that of free esterases of the rat's pancreas is due to a higher proportion of heat resistant slow carboxylesterases in the former. More significant differences in the heat resistance of pancreas and liver is caused not only by different heterogeneity of esterases, but also by their qualitative differences.

Animals↗