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At least 577 records · Page 32Linked to original sources
PubMed1995

The identification and partial characterisation of a novel inducible extracellular thermostable esterase from the archaeon Sulfolobus shibatae.

Extracellular esterases have so far only been reported in eubacteria, here we report the first identification and partial characterisation of a novel inducible extracellular esterase from the thermoacidophilic archaeon Sulfolobus shibatae. This esterase exhibits remarkable stability to both acid and heat. Esterase activity is induced by growth on a range of polyoxyethylenesorbitan (Tween) compounds as sole carbon source. Activity occurs over a wide temperature (25-99 degrees C) and pH (pH4.0-9.0) range and is optimal at 90 degrees C and pH6.0. It exhibits high thermal stability, with a half-life of 20 min at 120 degrees C, and shows a transient thermal activation of 60% at 90 degrees C. The thermal inactivation of function occurs by first order kinetics, and after 120 min incubation at 120 degrees C 50% of activity still remains. It is able to hydrolyse mono- and diglycerides, but is unable to hydrolyse the triglycerides olive oil and triolein, which is indicative of an esterase and not a lipase.

Enzyme Induction↗
PubMed1981

Circadian variation of liver esterases.

The circadian rhythm of liver esterase activity has been studied in rats maintained under highly standardized laboratory condition. They were housed in specially constructed climate rooms and subjected to an artificial 12 : 12 light-dark regimen. The total esterase was further differentiated to A esterase (E.C. 1.1.2) by using E 600 (Paraoxan), and a circadian rhythm for this enzyme also has been observed. During the lowest phase of total esterase activity, the higher phase for organophosphate-resistant esterase activity was observed.

Animals↗
PubMed1982

Organ specific expression of esterase-6 in the house mouse, Mus musculus.

Esterase-6 in fresh homogenates of heart muscle and testis of the house mouse shows a two band (C allele) or three band (A allele) pattern in disc electrophoresis. These primary bands generated in series of secondary bands upon lowering the pH of the homogenates, and the secondary pattern, possibly resulting from partial proteolysis, was seen in varying degrees in fresh homogenates from a range of organs. Interrelationships between the primary and secondary bands were demonstrated by isoelectric focusing. The esterase-6 content of twenty different organ homogenates was estimated from electrophoretic gels, and a high level of this enzyme was observed in those organs most actively involved in fat metabolism. The possible participation of esterase-6 in fatty acid utilization is discussed. Similarities between esterase-6 of the house mouse and esterase-4 of the rat were demonstrated, further strengthening the view that these enzymes are homologous.

Adipose Tissue↗
PubMed1980

Linkage conservation of homologous esterase loci in fish (Cyprinodontoidei: Poeciliidae).

Homologies among esterase isozymes in fish in the poeciliid genera Poeciliopsis and Xiphophorus are proposed. Esterase homologies are based on their tissue distributions and inhibition and substrate properties. The five esterases include two carboxylesterases, one eserine sulfate-sensitive esterase, and two esterases resistant to inhibition, one of which reacts only with acetate esters. Linkage studies in Poeciliopsis monacha indicate that the loci encoding the two carboxylesterases are linked to each other and to the locus for eye-specific lactate dehydrogenase. Comparisons of the linking reported here with earlier studies in Xiphophorus suggest that there is a large region of linkage homology in the genetic maps of Poeciliopsis and Xiphophorus.

Animals↗
PubMed1976

The effect of EDTA and metal cations on the 5-bromoindoxyl acetate esterase activity in the thyroid of the guinea pig.

Miscellaneous metal cations and EDTA have been used as activators and inhibitors of esterase activity in the thyroid of the guinea-pig. The results indicate that the 5-bromoiondoxyl acetate esterase in the epithelial cells probably consists of two different A-esterase isoenzymes, one present in group I cells (the para-, intra-, and inter-follicular cells) and the other in group II cells (the follicular cells proper). The first isoenzyme seems to be calcium-dependent whereas the other is activated by various metal ions. Ca2+ + Mn2+ and Ca2+ + Co2+ were found to activate the esterase activity in group I cells. EDTA and Mn2+, on the other hand, activated the esterase activity in group II cells.

Animals↗
PubMed1985

Cholesterol esterase activity of human intestinal mucosa.

It has been suggested that cholesterol absorption in humans is dependent on bile acid pool composition and that expansion of the cholic acid pool size is followed by an increase of the absorption values. Similar observations were reported in rats, where the increase of cholesterol absorption, after trihydroxy bile acid feeding, seems to be due to the stimulatory effect of cholic acid on the intestinal cholesterol esterase. In the present study, therefore, we investigated some general properties of human intestinal cholesterol esterase, with particular emphasis to the effect of bile acids on this enzymatic activity. Twenty-nine segments of small intestine were taken during operations; the enzymatic activity was studied by using mucosal homogenate as a source of enzyme and oleic acid, cholesterol, and 14C-labeled cholesterol as substrates. The time-activity relationship was linear within the first two hours; optimal pH for esterification ranged between 5 and 6.2. There was little difference between the esterifying activity of the jejunal and ileal mucosa. Esterification of cholesterol was observed with all the investigated fatty acids but was maximal with oleic acid. Bile acids did not affect cholesterol esterase activity when present in the incubation mixture at 0.1 and 1.0 mM; the enzymatic activity, however, was significantly inhibited when bile acids were added at 20 mM. In conclusion, this study has shown that the human intestinal mucosa possesses a cholesterol esterase activity; at variance with the rat, however, the human enzyme does not seem to be stimulated by trihydroxy bile acids. Thus, the stimulatory effect of cholic acid on cholesterol absorption induced by the administration of this bile acid does not seem to be simply due to changes of cholesterol esterase activity of the small bowel mucosa.

Adult↗
PubMed1996

Duplication and divergence of the genes of the alpha-esterase cluster of Drosophila melanogaster.

The alpha-esterase cluster of D. melanogaster contains 11 esterase genes dispersed over 60 kb. Embedded in the cluster are two unrelated open reading frames that have sequence similarity with genes encoding ubiquitin-conjugating enzyme and tropomyosin. The esterase amino acid sequences show 37-66% identity with one another and all but one have all the motifs characteristic of functional members of the carboxyl/cholinesterase multigene family. The exception has several frameshift mutations and appears to be a pseudogene. Patterns of amino acid differences among cluster members in relation to generic models of carboxyl/cholinesterase protein structure are broadly similar to those among other carboxyl/cholinesterases sequenced to date. However the alpha-esterases differ from most other members of the family in: their lack of a signal peptide; the lack of conservation in cysteines involved in disulfide bridges; and in four indels, two of which occur in or adjacent to regions that align with proposed substrate-binding sites of other carboxyl/cholinesterases. Phylogenetic analyses clearly identify three simple gene duplication events within the cluster. The most recent event involved the pseudogene which is located in an intron of another esterase gene. However, relative rate tests suggest that the pseudogene remained functional after the duplication event and has become inactive relatively recently. The distribution of indels also suggests a deeper node in the gene phylogeny that separates six genes at the two ends of the cluster from a block of five in the middle.

Amino Acid Sequence↗
PubMed2003

Molecular population genetics of the beta-esterase gene cluster of Drosophila melanogaster.

We have investigated nucleotide polymorphism at the beta-esterase gene cluster including the Est-6 gene and psiEst-6 putative pseudogene in four samples of Drosophila melanogaster derived from natural populations of southern Africa (Zimbabwe), Europe (Spain), North America (USA: California), and South America (Venezuela). A complex haplotype structure is revealed in both Est-6 and psiEst-6. Total nucleotide diversity is twice in psiEst-6 as in Est-6; diversity is higher in the African sample than in the non-African ones. Strong linkage disequilibrium occurs within the beta-esterase gene cluster in non-African samples, but not in the African one. Intragenic gene conversion events are detected within Est-6 and, to a much greater extent, within psiEst-6; intergenic gene conversion events are rare. Tests of neutrality with recombination are significant for the beta-esterase gene cluster in the non-African samples but not significant in the African one. We suggest that the demographic history (bottleneck and admixture of genetically differentiated populations) is the major factor shaping the pattern of nucleotide polymorphism in the beta-esterase gene cluster. However there are some 'footprints' of directional and balancing selection shaping specific distribution of nucleotide polymorphism within the cluster. Intergenic epistatic selection between Est-6 and psiEst-6 may play an important role in the evolution of the beta-esterase gene cluster preserving the putative pseudogene from degenerative destruction and reflecting possible functional interaction between the functional gene and the putative pseudogene. Est-6 and psiEst-6 may represent an indivisible intergenic complex ('intergene') in which each single component (Est-6 or psiEst-6) cannot separately carry out the full functional role.

Animals↗
PubMed2005

Genetic variation along time in a Brazilian population of Aedes aegypti (Diptera: Culicidae), detected by changes in the esterase patterns.

Aedes aegypti from the Brazilian cities of São José do Rio Preto (SJ) and Goiânia (GO) were analyzed as to their esterase patterns and the results were compared with data obtained about 5 years before for SJ population. Esterase bands not detected in the previous study were now observed in mosquitoes from both SJ and GO populations, being the last considered a population resistant to insecticides. Other similarities between SJ and GO populations in this study, and some differences in comparison with the previous data on SJ were observed, involving, in addition to changes in band type, changes in frequency of mosquitoes expressing them and differential gene activation during development. As it is generally true for genetic features, changes in the esterase patterns are expected to be the result of factors such as selection by environmental conditions and genetic drift. In the present case, continuous use of insecticides aiming mosquito population size control in SJ by sanitary authorities could be involved in the observed changes. Changed esterases were classified as carboxylesterases and cholinesterases, which are enzymes already shown to take part in the development of resistance in several organisms. In addition, data obtained in the elapsed time by authorities responsible for the mosquito control has shown increasing insecticide resistance of SJ population mosquitoes parallel to increase in the total amount of esterases, reinforcing the mentioned possibility.

Aedes↗
PubMed1989

Esterase activity in second- and third-trimester amniotic fluid: an indicator of chorioamnionitis.

Accurate and rapid diagnosis of chorioamnionitis poses a major diagnostic dilemma. We previously reported that leukocyte esterase activity in amniotic fluid, as measured by dipstick assay, could be used as an aid in the diagnosis of chorioamnionitis. This study examines the effectiveness of an in vitro spectrophotometric assay of esterase activity in amniotic fluid. We define baseline levels of esterase activity in uninfected amniotic fluid and demonstrate a quantitative increase when infection is present. Fifty-seven amniotic fluid samples obtained at second- and third-trimester amniocenteses were divided into three parts, one for culture and two for a comparison of esterase activities by the dipstick and spectrophotometric methods. In this study, the spectrophotometric assay, because of its higher specificity and sensitivity in the determination of elevated esterase activity, was shown to be more reliable for predicting chorioamnionitis than either the dipstick or culture method.

Amniocentesis↗
PubMed1983

Acylhydrolases from parsley (Petroselinum hortense). Relative distribution and properties of four esterases hydrolyzing malonic acid hemiesters of flavonoid glucosides.

In parsley, malonylated flavonoid glycosides are formed in response to ultraviolet irradiation and accumulate in the vacuoles. Involvement of malonyltransferases, which catalyze the transfer of malonic acid from malonyl-coenzyme A to either flavone/flavonol 7-O-glucosides or flavonol 3-O-glucosides, has been described previously. These enzymes are present in very young leaf buds, and their activities decrease rapidly when leaves begin to unfold, while at the same time esterase activity is developing. The latter enzyme activity continues to increase with tissue age. Four esterases, distinguished by pI's of 3.8, 3.9, 4.0, and 4.05, were purified to apparent homogeneity from parsley leaves and shown to hydrolyze malonic acid hemiesters of flavonoid glucosides. These esterases are unspecific and are best described as one acetyl- and three arylesterases on the basis of inhibition studies by 4-chloromercuribenzoic acid and diisopropyl fluorophosphate. Esterases and malonic acid hemiesters appear to be separated from each other within the parsley leaf cell, and only on disruption of the cells do the respective substrates become available to the enzymes. Involvement of esterases in formation of wound periderm in parsley plants is suggested.

Acyltransferases↗
PubMed1994

Solubilization and purification of A-esterase from mouse hepatic microsomes.

A-esterase(s), an enzyme(s) that hydrolyzes certain organophosphate compounds, is located in mammals, primarily in serum and liver. Although considerable information is available regarding serum A-esterase(s), little is known about the hepatic form(s) of this enzyme. In the present study, hepatic A-esterase activity was quantified by measuring the EDTA-sensitive hydrolysis of the organophosphate paraoxon (O,O-diethyl-O-p-nitrophenyl phosphate). EDTA-insensitive hydrolysis was assumed to be the nonenzymatic phosphorylation of proteins with appropriate serine hydroxyl groups. Resuspension of mouse hepatic microsomes in 50 mM potassium phosphate buffer, pH 7.4, containing 100 microM calcium chloride, 0.25% sodium cholate, and 0.1% Triton N-101, resulted in the solubilization of A-esterase activity, as evidenced by the failure of activity to sediment after centrifugation at 100,000 g for 1 hr. Gel permeation chromatography followed by ion-exchange chromatography and nonspecific affinity chromatography resulted in a peak of A-esterase activity judged to be homogeneous by SDS-PAGE. A typical purification resulted in a 1531-fold increase in specific activity, with a recovery of 10%. SDS-PAGE with and without an acrylamide gradient indicated a molecular weight of 40,000 and 39,000 Da, respectively, while analyses of amino acid composition revealed similarities with human and rabbit serum paraoxonase. And finally, although this protein hydrolyzed both paraoxon and methyl paraoxon (O,O-dimethyl-O-p-nitrophenyl phosphate), it did not hydrolyze p-nitrophenyl acetate.

Amino Acids↗
PubMed1978

Effects of carcinogenic and non-carcinogenic chemicals on plasma esterases in BALB/c mice.

Esterase profiles of plasma from female BALB/c mice treated with a variety of carcinogenic and weakly- or non-carcinogenic chemicals were analyzed. Mice treated with the potent carcinogens diethylnitrosamine, dinitrosopiperazine, dipropylnitrosamine, dimethylhydrazine, urethane, and dimethyldinitrosopiperazine had similarly altered plasma esterase profiles after 7 days' exposure to the chemicals. The alterations consisted of increased activity in 4 esterase bands. The increased activity persisted in some of the bands after cessation of carcinogen exposure. Exposure to high concentrations of the weakly- or non-carcinogenic compounds nitrosohydroxyproline, nitrosomethoxymethylamine, 1-nitroso-4methylpiperazine,nitroso-2,6dimethylpiperidine, and ethyl methanesulfonate caused no obvious plasma esterase alterations. Ingestion of carbon tetrachloride resulted in increased activity in one esterase band with concomitant decrease in a second band. Analysis of serum from test mice for levels of serum glutamic oxaloacetic transaminase, alkaline phosphatase, lactate dehydrogenase-lactate substrate, and D-gamma-glutamyl transpeptidase did not differentiate between mice treated with selected carcinogens and those treated with non-carcinogens and/or carbon tetrachloride.

Animals↗
PubMed1990

Sequence identity between human pancreatic cholesterol esterase and bile salt-stimulated milk lipase.

Three overlapping cDNA clones covering the entire primary sequence of the bile salt stimulated lipase in human milk were isolated from a human breast lambda gt10 cDNA library by screening with the rat pancreatic cholesterol esterase cDNA. Nucleotide sequencing of the cDNA showed that the human milk lipase mRNA encodes a 748-residue protein, including a 23-residue signal peptide. The human milk lipase cDNA is highly homologous to rat pancreatic cholesterol esterase, suggesting that the milk lipase may be identical to the cholesterol esterase in human pancreas. This conclusion was confirmed by isolation and sequencing of the cDNA for human pancreatic cholesterol esterase. Analysis of the sequence for the human cholesterol esterase/milk lipase revealed similarities to other serine esterases in three distinct regions of the protein. These domains may represent the active site triads of these proteins.

Amino Acid Sequence↗
PubMed1991

Involvement of a serine esterase in oxidant-mediated activation of phospholipase A2 in pulmonary endothelium.

Exposure of bovine pulmonary arterial endothelial cells to 1 mM H2O2 stimulated associated TAME-esterase and PLA2 activities. Pretreatment with the serine esterase inhibitors: PMSF (1 mM), DFP (1 mM), and alpha 1-PI (1 mg/ml) inhibited H2O2-induced stimulation of TAME-esterase and PLA2 activities. The TAME-esterase and PLA2 activities under H2O2 exposure were determined to be linearly correlated. Affinity labelling of the endothelial cell membrane with [3H]DFP demonstrated that the serine esterase resides in a protein having molecular weight of 29,000 daltons (29 kDa) which is similar to that of elastase. Treatment of the endothelial cell homogenate with trypsin (1 microgram/ml) also stimulated PLA2 activity.

Animals↗
PubMed1995

The expression of esterase S gene of Drosophila virilis in Drosophila melanogaster.

Drosophila melanogaster was transformed with the esterase S gene from Drosophila virilis. This gene is strongly activated in ejaculatory bulbs of mature males of Drosophila virilis. The closely related gene from Drosophila melanogaster is activated in ejaculatory ducts. The tissue- and stage-specific expression of incomplete genomic copy of the esterase S gene integrated into the Drosophila melanogaster genome is the same as in Drosophila virilis. These data show that tissue and stage specificity is determined by relatively small 5' regulatory region of the esterase S gene. The comparison between deduced amino-acid sequences of the esterase S of Drosophila virilis and esterase 6 of Drosophila melanogaster was performed. These sequences revealed 50% homology.

Amino Acid Sequence↗
PubMed1978

The activities of urinary alpha-esterases in bilharziasis and their possible role in the diagnosis of bilharzial bladder cancer in Egypt.

The activities of serum and urinary alpha-esterases were studied in 49 bilharzial bladder cancer patients, 92 bilharzial patients with other, different, urologic diseases and 22 normal healthy controls. Among the group studied, the bilharzial bladder cancer patients showed the highest level of urinary-alpha-esterases and the lowest ratio of serum/urine activity. These patients showed a significant increase in the activity of urinary alpha-esterases as compared with the normal controls or with the other different bilharzial groups. Although a small but significant increase in serum activity was observed in all the bilharzial groups studied compared with the normal healthy controls, no significant difference was found between the bilharzial bladder cancer patients and the other different bilharzial groups. Biochemical determination of urinary alpha-esterases for bilharzial patients revealed a high degree of accuracy for the diagnosis of bilharzial bladder cancer (95.9%), with low falsely positive (3.26%) and falsely negative (4.08%) results. The activity of urinary alpha-esterases in recommended as a screening test for bilharzial bladder cancer.

Egypt↗
PubMed1992

Esterase activity in human breast cyst fluid: associations with steroid sulfates and cations.

Human breast cyst fluid (BCF) contains an esterase that on the basis of electrophoretic mobility and response to inhibitors differs from those found in the plasma. From a total of 384 BCF samples analyzed for esterase using p-nitrophenyl hexanoate as substrate, 149 (39%) showed significant activity. The samples had been analyzed for the concentrations of the sulfates of estrone, estriol, dehydroepiandrosterone, as well as the potassium and sodium cations (K+/Na+). The data were submitted to statistical analysis using the Spearman rank order test. The esterase-positive samples exhibited a significant positive association with each of the steroid sulfates and the K+/Na+ ratios. Except for protein concentration, there was no significant correlation between the esterase-positive and esterase-negative cysts. These observations may have physiological significance in that high K+/Na+ ratio cysts have been related to the histological status of the cyst.

Biomarkers↗