SEARCH · Search PubMed

Results for “ESTERASES”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,693 records · Page 94Linked to original sources

PubMed1980

In vivo and in vitro studies of inhibitory effects of restorative dental materials on salivary esterases.

The influence of 18 dental materials on the activity of esterases isolated from human whole saliva has been studied. Eugenol on its own was a strong competitive inhibitor of the esterases II-2a (Ki = 3.3/10(-5) M) and II-2b (Ki = 4.7/10(-6) M). Except for Luralite all the materials that contained eugenol as one of the components (IRM, Nobetec and Opotow) were noncompetitive inhibitors. Additional in vitro inhibitors were: Adaptic, Aspa, Coe-pack and the amalgam ANA 68. Treatment with Nobetec packs in vivo resulted in a decrease activity of whole saliva.

Dental Materials↗

PubMed1981

Esterases in schistosomes: reaction with substrates and inhibitors.

Studies were made (at 37 degrees, pH 7.6) on the interaction of some organophosphorus compounds and carboxylic acid esters with cholinesterases (EC 3.1.1.7 and EC 3.1.1.8) and A-esterases (EC 3.1.1.2) in homogenates of Schistosoma mansoni (adults and cercariae) and Schistosoma haematobium (adults). The results are compared with those obtained from the same reactions in other parasitic helminths and in mammalian tissues. Metrifonate (0,0-dimethyl-2,2,2-trichloro-1-hydroxyethyl phosphonate) does not seem to react with cholinesterases from parasites or mammals. Dichlorvos (0,0-dimethyl-2,2-dichlorovinyl phosphate) is a phosphorylating inhibitor; the rate constants of inhibition of cholinesterases from schistosomes are in the order of 10(5) M-1 min.-1. Similar or lower rate constants (10(4) M-1 min.-1) are found for cholinesterase inhibition in other parasitic helminths and mammals. S. mansoni and S. haematobium hydrolyse carboxylic acid esters (10 mM) in decreasing order: phenylacetate (about 2 mumol per hour per mg protein), acetylthiocholine, propionylthiocholine, butyrylthiocholine. Dichlorvos (10 mM) is hydrolysed by S. mansoni and S. haematobium at about the same rate as by mammalian erythrocytes and human sera (about 10 mumol per hour per gram wet weight). Neither paraoxon (0,0-diethyl-4-nitrophenyl phosphate) nor methyl-paraoxon are hydrolysed by S. mansoni and S. haematobium, although both compounds are good substrates for mammalian A-esterases. The stability of metrifonate and dichlorvos in buffer solutions was also determined (at 37 degrees). Metrifonate is about equally stable in bicarbonate buffer (pH 7.6) and phosphate buffer (pH 7.4) (t 1/2 = 1.5 and 2.6 hrs, respectively), while dichlorvos is considerably more stable in bicarbonate (t 1/2 = (36 hrs) than in phosphate buffer (t 1/2 = 2.9 hrs).

Animals↗

PubMed1993

Geographical clinal variation at seven esterase-coding loci in Indian populations of Zaprionus indianus.

Twelve Indian natural populations of Zaprionus indianus, collected along 22 degrees latitudinal range, were analysed electrophoretically for allozymic variation of esterase gene-enzyme system. Interestingly, all the seven Est loci were found to be highly polymorphic in all the populations of Z. indianus. The genetic structure of Z. indianus populations was characterized by extensive inter-populational genotypic as well as allelic frequency heterogeneity and higher genic differentiation at all the esterase-coding loci. All the polymorphic loci in geographical populations of Z. indianus revealed latitudinal clines, and changes in allelic frequencies were found to correlate with latitude. The occurrence of higher genetic variability in Z. indianus populations was in agreement with its habitat-generalist or broad niche-width characteristics, i.e., the species populations utilized diverse food resources and displayed adaptation to variable climatic conditions. Thus, the observed genic divergence patterns in colonizing populations of Z. indianus could be maintained by balancing natural selection varying spatially along the north-south axis of the Indian sub-continent.

Animals↗

PubMed1981

Malignant thymus tumour progressing into acute leukaemia with non-specific esterase activity.

We describe an 8-year-old girl who presented a massive mediastinal tumour of thymic origin. Surgical excision was unsuccessful. Irradiation treatment (4,500 rad) together with intensive combination chemotherapy resulted in regression of the tumour. After three months, an increase of blasts was observed in the peripheral blood and bone marrow. The terminal phase was characterized by acute leukaemia, which did not respond to chemotherapy. Despite the thymic origin of this malignancy, the blast cells contained non-specific esterase activity as determined by naphthol-AS-acetate as substrate. The NaF-sensitive form of this enzyme is a characteristic of monocytes-macrophages. Other monocyte-macrophage markers were, however, negative. We conclude that the NaF-sensitive naphthol-AS-acetate esterase is not limited to tumours of the monocyte-macrophage system.

Bone Marrow Examination↗

PubMed1990

Equilibrium among hematoporphyrin derivative components--II. Effect of esterase activity.

Photofrin II is the hematoporphyrin-derivative fraction enriched in covalently-linked oligomers, characterized by a high degree of folding. Interaction with hydrophobic structures, such as biomolecules and cell structures, results in a modification of the equilibria among the different species, as a consequence of an unfolding effect exerted towards the electrostatic aggregates. The effect of esterase activity was evaluated, taking into account the nature suggested for the covalent linkage of the oligomers (ether and/or ester). The study was performed in Photofrin II aqueous solution by means of absorption and fluorescence spectral analysis. The results showed that the esterase is active only towards the unfold oligomers: that is, in Photofrin II solution supplemented with albumin. In these conditions, spectral analysis revealed the presence of a monomerization process, which is clearly evident during the first four hours of incubation. The monomerization effect induced by the enzyme was also proven by both equilibrium-dialysis measurements and zinc ion complexation. Zinc ion complexes with high affinity for monomeric species, giving rise to a very distinct emission band at 580 nm. The amount of ester linkage shown in the oligomers through enzyme hydrolysis appeared to be less than might have been expected, owing to the inhibiting effect of the monomer produced on the enzyme. The results are a step toward clarifying the intracellular and intratissue turnover of the drug observed after administration.

Esterases↗

PubMed1994

Enhanced rectal absorption of itazigrel formulated with polysorbate 80 micelle vehicle in rat: role of co-administered esterase.

We investigated the effect of esterase on rectal absorption in the rat of itazigrel using polysorbate 80 (PS-80) micelle as a vehicle to overcome the poor aqueous solubility of itazigrel. The itazigrel formulation prepared with PS-80 increased the absorption compared with a 0.25% carmellose sodium suspension, probably by supplying the itazigrel solute to keep a high concentration at the epithelial surface. When esterase was co-administered with the formulations containing PS-80, the absorption of itazigrel from rat rectum was accelerated further, by rapid release of itazigrel from the micelle vehicle after enzymatic degradation of the PS-80 micelle.

Absorption↗

PubMed2005

Identification of esterases expressed in Caco-2 cells and effects of their hydrolyzing activity in predicting human intestinal absorption.

The absorption characteristics of temocapril were investigated using Caco-2 cells, and the esterases expressed in Caco-2 cells were identified. Temocapril was almost completely hydrolyzed to temocaprilat during transport across Caco-2 cells. Hydrolysis experiments of temocapril in Caco-2 cell 9000g supernatant (S9) and brush-border membrane vesicles showed that temocapril was mainly hydrolyzed within the cells after uptake, after which the temocaprilat formed was transported to both the apical and basolateral surfaces. In native polyacrylamide gel electrophoresis by detection of hydrolase activity for 1-naphthylbutyrate, Caco-2 cell S9 showed a band with high esterase activity and another band with extremely low activity. The proteins in the major and minor bands were identified as carboxylesterase-1 (hCE-1) and carboxylesterase-2 (hCE-2). The abundant expression of hCE-1 in Caco-2 cells was supported by reverse transcription-polymerase chain reaction. In the normal human small intestine, hCE-2 is abundantly present, although the human liver expresses much higher levels of hCE-1 and lower levels of hCE-2. The expression pattern of carboxylesterases in Caco-2 cells is completely different from that in human small intestine but very similar to that in human liver. Since the substrate specificity of hCE-1 differs from that of hCE-2, it is suggested that the prediction of human intestinal absorption using Caco-2 cell monolayers should be performed carefully in the case of ester- and amide-containing drugs such as prodrugs.

Caco-2 Cells↗

PubMed1962

New genetically determined molecular form of erythrocyte esterase in man.

An altered molecular form of erythrocyte esterase was discovered in hemolysates from two males and one female in three generations of the same family. This indicates that the alternate enzyme form is under the control of a single autosomal gene. Evidence suggests that the atypical esterase is a variant form of erythrocyte carbonic anhydrase.

Carbonic Anhydrases↗

PubMed1967

Esterase polymorphism in natural populations of a sulfur butterfly, Colias eurytheme.

Starch-gel electrophoresis of esterases of wild and laboratoryreared individuals of Colias eurytheme indicates that populations in central Texas are exceedingly variable, consisting almost entirely of heterozygotes formed from a large number of alleles at an autosomal locus controlling the production of an esterase designated EST E. Few wild individuals are genetically identical at this locus. The commonest member of the allelic series is an apparent null allele that results in no EST E activity.

Animals↗

PubMed1973

Pyrethroid insecticides: esterase cleavage in relation to selective toxicity.

The ester group of primary alcohol chrysanthemates is cleaved by mouse hepatic microsomal esterases, more rapidly for the (+)-trans than for the (+)-cis isomers. Substrate-specificity and inhibition studies in vivo establish that these pyrethroid-hydrolyzing esterases probably contribute to the low mammalian toxicity of bioresmethrin and other (+)-trans chrysanthemate insecticide chemicals derived from primary alcohols.

Animals↗

PubMed1973

Esterase, malate, and lactate dehydrogenases activity in murine neuroblastoma.

Mouse neuroblastoma tumors have only the fifth isozyme band (A(4)) of lactate dehydrogenase, whereas this band is missing in the brain which contained four other bands of lactate dehydrogenase. The alpha-esterase isozyme patterns of tumors, kidney, and brain are similar except that there is an additional slowest-moving form of esterase in all tumor tissues. The malate dehydrogenase pattern is not altered in any of the tissues.

Animals↗

PubMed1986

Amplification of an esterase gene is responsible for insecticide resistance in a California Culex mosquito.

An esterase gene from the mosquito Culex quinquefasciatus that is responsible for resistance to a variety of organophosphorus (OP) insecticides was cloned in lambda gt11 phage. This gene was used to investigate the genetic mechanism of the high production of the esterase B1 it encodes in OP-resistant Culex quinquefasciatus Say (Tem-R strain) from California. Adults of the Tem-R strain were found to possess at least 250 times more copies of the gene than adults of a susceptible strain (S-Lab). The finding that selection by pesticides may result in the amplification of genes encoding detoxifying enzymes in whole, normally developed, reproducing insects emphasizes the biological importance of this mechanism and opens new areas of investigation in pesticide resistance management.

Animals↗

PubMed1980

Regional assignment of genes for human esterase D and retinoblastoma to chromosome band 13q14.

The expression of human esterase D was evaluated quantitatively and qualitatively in five persons with partial deletions or duplications of chromosome 13. The results showed that the locus of this enzyme is at band 13q14. Deletion of this same band in other subjects has been found previously to indicate a predisposition to the development of retinoblastoma, which was present in the four individuals in this study who had partial deletions of chromosome 13. Because of this close synteny, esterase D evaluation should aid in the diagnosis and genetic counseling of retinoblastoma.

Chromosome Deletion↗

PubMed2006

Rapid degradation of oseltamivir phosphate in clinical samples by plasma esterases.

The anti-influenza drug oseltamivir is an ester prodrug activated by hepatic carboxylesterases. Plasma esterases also convert up to 31.8% of the parent compound to the active metabolite after 4 h ex vivo, with wide interindividual variation. This source of error is removed by adding the esterase inhibitor dichlorvos to blood collection tubes.

Adult↗

PubMed1995

Characterization of uptake and hydrolysis of fluorescein diacetate and carboxyfluorescein diacetate by intracellular esterases in Saccharomyces cerevisiae, which result in accumulation of fluorescent product.

Flow cytometry is a rapid and sensitive method which may be used for the detection of microorganisms in foods and drinks. A key requirement for this method is a sufficient fluorescence staining of the target cells. The mechanism of staining of the yeast Saccharomyces cerevisiae by fluorescein diacetate (FDA) and 5- (and 6-)carboxyfluorescein diacetate (cFDA) was studied in detail. The uptake rate of the prefluorochromes increased in direct proportion to the concentration and was not saturable, which suggests that transport occurs via a passive diffusion process. The permeability coefficient for cFDA was 1.3 x 10(-8) m s-1. Once inside the cell, the esters were hydrolyzed by intracellular esterases and their fluorescent products accumulated. FDA hydrolysis (at 40 degrees C) in cell extracts could be described by first-order reaction kinetics, and a rate constant (K) of 0.33 s-1 was calculated. Hydrolysis of cFDA (at 40 degrees C) in cell extracts was described by Michaelis-Menten kinetics with an apparent Vmax and Km of 12.3 nmol.min-1.mg of protein-1 and 0.29 mM, respectively. Accumulation of fluorescein was most likely limited by the esterase activity, since transport of FDA was faster than the hydrolysis rate. In contrast, accumulation of carboxyfluorescein was limited by the much slower transport of cFDA through the cell envelope. A simple mathematical model was developed to describe the fluorescence staining. The implications for optimal staining of yeast cells with FDA and cFDA are discussed.

Biological Transport, Active↗

PubMed1997

Molecular analysis of the Rhodococcus sp. strain H1 her gene and characterization of its product, a heroin esterase, expressed in Escherichia coli.

The structural gene for heroin esterase was cloned from Rhodococcus sp. strain H1 and expressed in Escherichia coli BL21(DE3). The purified enzyme was found to be a tetramer with an M(r) of 137,000 and an apparent K(m) of 0.88 mM for 6-acetylmorphine. The G-x-S-x-G motif was observed in the deduced amino acid sequence, suggesting that the enzyme is a serin esterase.

Acetylesterase↗

PubMed1999

Purification and properties of an esterase from the yeast Saccharomyces cerevisiae and identification of the encoding gene.

We purified an intracellular esterase that can function as an S-formylglutathione hydrolase from the yeast Saccharomyces cerevisiae. Its molecular mass was 40 kDa, as determined by gel filtration and sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The isoelectric point was 5.0 by isoelectric focusing. The enzyme activity was optimal at 50 degrees C and pH 7.0. The corresponding gene, YJLO68C, was identified by its N-terminal amino acid sequence and is not essential for cell viability. Null mutants have reduced esterase activities and grow slowly in the presence of formaldehyde. This enzyme may be involved in the detoxification of formaldehyde, which can be metabolized to S-formylglutathione by S. cerevisiae.

Esterases↗

PubMed2002

Fusarium Tri8 encodes a trichothecene C-3 esterase.

Mutant strains of Fusarium graminearum Z3639 produced by disruption of Tri8 were altered in their ability to biosynthesize 15-acetyldeoxynivalenol and instead accumulated 3,15-diacetyldeoxynivalenol, 7,8-dihydroxycalonectrin, and calonectrin. Fusarium sporotrichioides NRRL3299 Tri8 mutant strains accumulated 3-acetyl T-2 toxin, 3-acetyl neosolaniol, and 3,4,15-triacetoxyscirpenol rather than T-2 toxin, neosolaniol, and 4,15-diacetoxyscirpenol. The accumulation of these C-3-acetylated compounds suggests that Tri8 encodes an esterase responsible for deacetylation at C-3. This gene function was confirmed by cell-free enzyme assays and feeding experiments with yeast expressing Tri8. Previous studies have shown that Tri101 encodes a C-3 transacetylase that acts as a self-protection or resistance factor during biosynthesis and that the presence of a free C-3 hydroxyl group is a key component of Fusarium trichothecene phytotoxicity. Since Tri8 encodes the esterase that removes the C-3 protecting group, it may be considered a toxicity factor.

Cell-Free System↗