Search PubMed⌕ Search

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.

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

At least 1,153 records · Page 64Linked to original sources
PubMed1994

Characterization of esterase and alcohol dehydrogenase activity in skin. Metabolism of retinyl palmitate to retinol (vitamin A) during percutaneous absorption.

Retinyl palmitate, a widely used ingredient in cosmetic products, is promoted for its beneficial effects on the appearance of skin. Previous studies suggest that enzymes are available in skin to metabolize this ingredient during skin absorption. Esterase activity hydrolyzes retinyl palmitate to retinol (vitamin A), which is oxidized in many tissues to retinoic acid primarily by alcohol dehydrogenase. The activities of esterase and alcohol dehydrogenase were characterized in hairless guinea pig skin by using flow-through diffusion cells and radiolabeled model compounds (methyl salicylate and benzyl alcohol) previously shown to be metabolized by these enzymes. Methyl salicylate was hydrolyzed by esterase to a greater extent in viable skin than in nonviable skin. Glycine conjugation of salicylic acid and benzoic acid occurred only in viable skin. The metabolism of methyl salicylate and benzyl alcohol occurred to a greater extent in male guinea pig skin than in female guinea pig skin. The percutaneous absorption of both radiolabeled compounds was similar in viable and nonviable skin. About 30 and 18% of topically applied retinyl palmitate were absorbed from an acetone vehicle by hairless guinea pig skin and human skin, respectively. Less than 1% of the applied dose of this lipophilic compound diffused from skin into the receptor fluid. Retinol was the only detectable metabolite of retinyl palmitate in both hairless guinea pig and human skin. In human skin, 44% of the absorbed retinyl palmitate was hydrolyzed to retinol. The use of retinyl palmitate in cosmetic formulations may result in significant delivery of retinol into the skin.

Alcohol Dehydrogenase↗
PubMed2003

A tripod ligand as new sensitiser for the enzyme amplified lanthanide luminescence determination of esterase.

Screening of a small library of tripod ligands resulted in the discovery of bis(2-pyridylmethyl)-(2-hydroxybenzyl)amine (HL1) as a new sensitiser, which is able to transfer its excitation energy to terbium(III). After synthesis of the acetic acid ester of HL1, a highly selective method for the determination of porcine liver esterase by means of enzyme amplified lanthanide luminescence (EALL) was developed. Enzyme-catalysed cleavage of the ester results in the formation of HL1. After excitation at 297 nm, the characteristic emission of Tb(III) at 545 nm is observed and used to determine the esterase concentration. In contrast to existing EALL methods, this method may be carried out at neutral pH and without further additives. Limit of detection for porcine liver esterase is 10(-9) mol l(-1) and limit of quantification is 3 x 10(-9) mol l(-1). A linear calibration range of two decades starting at the limit of quantification is observed.

Animals↗
PubMed1982

Regulation of neutral cholesterol esterase and acyl-CoA : cholesterol acyltransferase in the rat adrenal gland.

The activities of neutral cholesterol esterase and acyl-CoA : cholesterol acyltransferase in rat adrenal gland were measured at various time intervals over 24 h. The activity of cholesterol esterase displayed diurnal rhythm, with a major peak at the onset of darkness coinciding with the peak in the diurnal rhythm of plasma corticosterone concentration. The activity of acyl-CoA : cholesterol acyltransferase also exhibited a characteristic diurnal rhythm, with the minimum activity occurring 3 h after the onset of darkness. The profile of the rhythm exhibited by the activity of the esterifying enzyme was similar to the mirror image of the pattern of diurnal rhythm in the activity of 3-hydroxy-3-methylglutaryl-CoA reductase. Microsomal non-esterified cholesterol showed a gradual decline with a significant decrease in concentration at the onset of darkness, thus suggesting that diurnal removal of cholesterol in the environment of the esterifying enzyme and hydroxymethylglutaryl-CoA reductase leads to such diurnal decrease or increase in the activities of these two enzymes. Acute administration of corticotropin led to a 3-fold increase in the activity of cholesterol esterase, a 50% decrease in the activity of acyl-CoA : cholesterol acyltransferase and a 2-fold increase in the activity of hydroxymethylglutaryl-CoA reductase. Corticotropin administration also resulted in a significant decrease in microsomal non-esterified cholesterol and increase in plasma corticosterone concentration. These observations suggest that corticotropin plays an important part in generating the diurnal rhythm in the activities of the three enzymes.

Acyltransferases↗
PubMed1993

Cloning and analysis of the esterase genes conferring insecticide resistance in the peach-potato aphid, Myzus persicae (Sulzer).

Full-length cDNA clones encoding the esterases (E4 and FE4) that confer insecticide resistance in the peach-potato aphid [Myzus persicae (Sulzer)] were isolated and characterized. The E4 cDNA contained an open reading frame of 1656 nucleotides, coding for a protein of 552 amino acids. The FE4 cDNA shared 99% identity with E4 over this region, the most important difference being a single nucleotide substitution resulting in the FE4 mRNA having an extra 36 nucleotides at the 3' end. The derived amino acid sequences for the N-terminus of E4 and FE4 were identical, with the first 23 residues being characteristic of a signal peptide and the next 40 residues being an exact match to the N-terminal sequence determined by Edman degradation of both purified proteins. The predicted molecular masses of 58.8 and 60.2 kDa for the E4 and FE4 polypeptides were consistent with those previously observed by in vitro translation of mRNA. Five potential N-linked glycosylation sites were present in both polypeptides, in accordance with earlier evidence that the native esterases are glycoproteins. Comparison of the aphid esterase protein sequences with other serine hydrolases provided evidence that their activity involves a charge-relay system with a catalytic triad the same as that found in acetylcholinesterase. Restriction mapping and sequencing of cloned genomic DNA showed that the E4 gene is spread over 4.3 kb with six introns and that the previously reported differences between the 3' ends of the E4 and FE4 genes result from single nucleotide substitutions and not gross differences in the DNA sequences.

Amino Acid Sequence↗
PubMed1996

Analysis of amplicons containing the esterase genes responsible for insecticide resistance in the peach-potato aphid Myzus persicae (Sulzer).

The amplification of genes encoding an insecticide-detoxifying esterase (E4) in the peach-potato aphid Myzus persicae is one of the few examples where this genetic phenomenon has been shown to be involved in the response of an intact higher organism to artificial selection. Here we report quantitative and qualitative studies of the repeat units (amplicons) containing the E4 genes in a highly resistant aphid clone. Initial studies to quantify esterase sequences showed a 5-11-fold increase in resistant aphids compared with susceptible aphids, suggesting the presence of 10-22 gene copies per diploid genome. A more incisive analysis by pulsed-field gel electrophoresis confirmed the presence of about 12 copies of the E4 gene and showed them to be on about 24 kb amplicons, arranged as a tandem array of direct repeats. This, together with previous results from crossing experiments and with recent in situ hybridization studies, confirms that the E4 gene amplification in this aphid clone is heterozygous at a single locus. However, these data show that the gene amplification alone cannot account for the approx. 60 times higher levels of E4 protein and its mRNA present in this aphid clone, and therefore resistance must involve changes in both esterase gene copy number and gene expression.

Animals↗
PubMed1998

Amplification of a serine esterase gene is involved in insecticide resistance in Sri Lankan Culex tritaeniorhynchus.

Culex tritaeniorhynchus, the major vector of Japanese encephalitis in Sri Lanka, is resistant to organophosphorus insecticides, with a 10-fold resistance ratio at the LC50 for chlorpyrifos, and a high heterogenelty factor in the insect field population. The major mechanism of resistance in this species, as in the mosquito C. quinquefasciatus, is elevation of esterase activity. Basic biochemical, immunological and molecular analysis suggests that the C. tritaeniorhynchus CtrEstbeta1 gene is orthologous to the C. quinquefasciatus amplified Estbetas. The Estbeta2(1) antiserum cross-reacts strongly with CtrEstbeta1(1). Its corresponding cDNA, over the 545 base pairs sequenced, has approximately 84% identity with the various C. quinquefasciatus Estbetas. The gene is amplified in C. tritaeniorhynchus. Amplification of the same esterase in two independent species, along with multiple amplification events involving this esterase gene in C. quinquefasciatus suggests that the location of this gene within the genome predisposes it to amplification.

Animals↗
PubMed1999

Elevated oxidase and esterase levels associated with permethrin tolerance in Anopheles gambiae from Kenyan villages using permethrin-impregnated nets.

The permethrin tolerance (PT) of a population of the mosquito Anopheles gambiae (Diptera: Culicidae) increased following the introduction of permethrin-impregnated nets for malaria control in certain villages near Kisumu, western Kenya. Using a biochemical test that indirectly measures oxidases associated with permethrin resistance, we found that this population had higher oxidase levels than a comparison population from villages without impregnated nets. Mosquitoes from a colony of An. gambiae selected for PT, the RSP (reduced susceptibility to permethrin) strain, were exposed to permethrin with or without the oxidase inhibitor piperonyl butoxide (PB). Significantly higher mortality rates occurred when permethrin was synergized by PB, presumably by suppression of oxidases responsible for PT. An unselected (UNS) colony of An. gambiae that was more susceptible than RSP in a permethrin-susceptibility bioassay (i.e. LT50 22 min for UNS, vs. 42min for RSP) was compared with the RSP colony for levels of oxidases and esterases. The levels of both enzymes were very significantly higher in the RSP strain (P<0.0001). We speculate that use of impregnated nets selected for higher oxidase and esterase levels in An. gambiae to metabolize permethrin acquired from the nets. Both oxidase and esterase mechanisms could confer cross-resistance to other pyrethroids.

Animals↗
PubMed1984

Enhancement in cholesterol-esterase activity and lipolysis due to 17 beta-estradiol treatment in rat adipose tissue.

The effects of 17 beta-estradiol and testosterone administration on cholesterol esterase, lipoprotein lipase activities and adrenalin-induced lipolysis were examined in rat adipose tissues with the change in serum lipid level. The administration of 17 beta-estradiol (500 micrograms/kg, 2 or 4 weeks) to male rats significantly reduced the body weight, and markedly increased serum cholesterol, triacylglycerols and phospholipids. Cholesterol esterase activity was significantly enhanced in the epididymal adipose tissue from estradiol treated rats and the effect was greater with duration of the treatment. In contrast, lipoprotein lipase activity was markedly reduced. Testosterone reduced cholesterol esterase activity in the parametrial adipose tissue through the treatment with 500 micrograms/kg for 6 weeks, but it did neither influence serum lipids nor lipoprotein lipase activity. Basal lipolysis and adrenalin-induced lipolysis were also significantly enhanced in the epididymal adipose tissue from the male rat treated either with 7 mg/kg estradiol 12 h ahead or with 500 micrograms/kg estradiol for 2 weeks. These results indicate that estradiol exerts strong effects on metabolism of the adipose and these effects seems to be mediated through cyclic-AMP. An alteration of adrenergic functions by gonadal steroids might be intervened.

Adipose Tissue↗
PubMed1976

Induction of human fibroblast proliferation by epidermal growth factor (EGF): enhancement by an EGF-binding arginine esterase and by ascorbate.

The effect of mouse epidermal growth factor (mEGF) and an mEGF-binding arginine esterase on the growth of cultured human fibroblasts has been studied. Physiological concentrations (10(-9)-10(-10) M) of the growth factor were found to stimulate DNA replication and cell proliferation in quiescent cultures, and the arginine esterase, which is normally associated with mEGF in vivo, was shown to enhance this growth effect synergistically. The cellular response to mEGF was dependent upon a low, growth-limiting concentration of serum in the extracellular medium. Ascorbic acid, which alone exhibited no growth-promoting effect, could partially replace this requirement, and was found to elicit a rapid and marked increase in proline hydroxylation. Quiescent cultures in serum-free medium containing ascorbic acid were stimulated by the combination of mEGF and the esterase in a manner comparable to that achieved with serum shift-up. The possible requirement of a collagen-containing extracellular matrix for the growth response to mEGF is discussed.

Ascorbic Acid↗
PubMed1994

9-O-acetylated sialic acids have widespread but selective expression: analysis using a chimeric dual-function probe derived from influenza C hemagglutinin-esterase.

While 9-O-acetylation of sialic acids has been reported in some mammalian tissues, the distribution of this modification on specific cell types and molecules is largely unknown. The influenza C virus hemagglutinin-esterase is a membrane-bound glycoprotein that binds specifically to 9-O-acetylated sialic acids (hemagglutinin activity) and then hydrolyzes the O-acetyl group (receptor-destroying activity). A recombinant soluble form of influenza C virus hemagglutinin-esterase wherein the C-terminal transmembrane and cytoplasmic domains are replaced by the Fc portion of human IgG retains both its recognition and enzymatic functions. The latter activity can selectively remove 9-O-acetyl groups from bound or free sialic acids and, under specific conditions, 7-O-acetyl groups as well. Irreversible inactivation of the esterase unmasks stable recognition activity, giving a molecule that binds specifically to 9-O-acetylated sialic acids. These probes demonstrate widespread but selective expression of 9-O-acetylated sialic acids in certain cell types of rat tissues. Patterns of polarized or gradient expression further demonstrate the regulated nature of this modification. Direct probing of blots and thin-layer plates shows selective expression of 9-O-acetylation on certain glycoproteins and glycolipids in such tissues. Thus, 9-O-acetylation is more widespread than previously thought and occurs on specific molecules and cell types.

Animals↗
PubMed1997

Phosphatidylcholine hydrolysis is required for pancreatic cholesterol esterase- and phospholipase A2-facilitated cholesterol uptake into intestinal Caco-2 cells.

Pancreatic secretion is required for efficient cholesterol absorption by the intestine, but the factors responsible for this effect have not been clearly defined. To identify factors involved and to investigate their role in cholesterol uptake, we studied the effect of Viokase(R), a porcine pancreatic extract, on cholesterol uptake into human intestinal Caco-2 cells. Viokase is capable of facilitating cholesterol uptake into these cells such that the level of uptake is 5-fold higher in the presence of solubilized Viokase. This stimulation is time-dependent and is dependent on the presence of bile salt. However, bile salt-stimulated pancreatic cholesterol esterase, which has been proposed to mediate cholesterol uptake, is not fully responsible. The major cholesterol transport activity was purified and identified as pancreatic phospholipase A2. Anti-phospholipase A2 antibodies abolished virtually all of the phospholipase A2 and cholesterol transport activity of solubilized Viokase. We demonstrate that both phospholipase A2 and cholesterol esterase increase cholesterol uptake by hydrolyzing the phosphatidylcholine that is used to prepare the cholesterol-containing micelles. In the absence of cholesterol esterase or phospholipase A2, uptake of cholesterol from micelles containing phosphatidylcholine is not as efficient as uptake from micelles containing phospholipase A2-hydrolytic products. These results indicate that phospholipase A2 may mediate cholesterol absorption by altering the physical-chemical state of cholesterol within the intestine.

Biological Transport↗
PubMed2002

Hormone-sensitive lipase is a cholesterol esterase of the intestinal mucosa.

The identity of the enzymes responsible for lipase and cholesterol esterase activities in the small intestinal mucosa is not known. Because hormone-sensitive lipase (HSL) catalyzes the hydrolysis of acylglycerols and cholesteryl esters, we sought to determine whether HSL could be involved. HSL mRNA and protein were detected in all segments of the small intestine by Northern and Western blot analyses, respectively. Immunocytochemistry experiments revealed that HSL was expressed in the differentiated enterocytes of the villi and was absent in the undifferentiated cells of the crypt. Diacylglycerol lipase and cholesterol esterase activities were found in the different segments. Analysis of gut from HSL-null mice showed that diacylglycerol lipase activity was unchanged in the duodenum and reduced in jejunum. Neutral cholesterol esterase activity was totally abolished in duodenum, jejunum, and ileum of HSL-null mice. Analysis of HSL mRNA structure showed two types of transcripts expressed in equal amounts with alternative 5'-ends transcribed from two exons. This work demonstrates that HSL is expressed in the mucosa of the small intestine. The results also reveal that the enzyme participates in acylglycerol hydrolysis in jejunal enterocytes and cholesteryl ester hydrolysis throughout the small intestine.

Animals↗
PubMed2006

Discrimination of esterase and peptidase activities of acylaminoacyl peptidase from hyperthermophilic Aeropyrum pernix K1 by a single mutation.

It has been shown that highly conserved residues that form crucial structural elements of the catalytic apparatus may be used to account for the evolutionary history of enzymes. Using saturation mutagenesis, we investigated the role of a conserved residue (Arg(526)) at the active site of acylaminoacyl peptidase from hyperthermophilic Aeropyrum pernix K1 in substrate discrimination and catalytic mechanism. This enzyme has both peptidase and esterase activities. The esterase activity of the wild-type enzyme with p-nitrophenyl caprylate as substrate is approximately 7 times higher than the peptidase activity with Ac-Leu-p-nitroanilide as substrate. However, with the same substrates, this difference was increased to approximately 150-fold for mutant R526V. A more dramatic effect occurred with mutant R526E, which essentially completely abolished the peptidase activity but decreased the esterase activity only by a factor of 2, leading to a 785-fold difference in the enzyme activities. These results provide rare examples that illustrate how enzymes can be evolved to discriminate their substrates by a single mutation. The possible structural and energetic effects of the mutations on k(cat) and K(m) of the enzyme were discussed based on molecular dynamics simulation studies.

Aeropyrum↗
PubMed1983

Kinetic and structural relationships of transition monomeric and oligomeric carboxyl- and choline-esterases.

The kinetic and structural relationships of eight electrophoretically pure mammalian serum and liver serine carboxylesterases (CE) and cholinesterases (ChE) have been studied. Eight CE's and ChE's, which were fully resolved but only partially purified, provided additional information. Five of the electrophoretically pure esterases were monomeric, and of these, four belonged to a new and widely distributed class. These four monomeric esterases hydrolyzed choline esters, but at widely differing rates. Thus two were termed monomeric butyrylcholinesterases, mBuChE I and II, and two were monomeric CE's (mCE). The rabbit liver mCE was not a subunit of the oligomeric CE (oCE), although the oCE also hydrolyzed choline esters at a very low rate. The complex kinetics of the mCE's, mBuChE's, oCE's, and of the oligomeric BuChE's of horse and human serum could be interpreted according to a single reaction scheme involving an allosteric site and the equation derived from it. Thus activation and inhibition at high substrate concentrations, together with sigmoidal activity versus substrate concentration plots, all of which characterize the reactions of these esterases, could be interpreted by a single scheme and equation. Structural and kinetic comparisons showed a progressive transition of properties from the oCE's through the mCE's to the oBuChE's. One of the purified mCE's was from horse serum, and it exhibited physical and kinetic properties unlike those of the liver mCE's or oCE's.

Allosteric Site↗
PubMed1969

The inhibition of plasmin, plasma kallikrein, plasma permeability factor, and the C'1r subcomponent of the first component of complement by serum C'1 esterase inhibitor.

The fraction of human serum designated as C'1 esterase inhibitor is known to inhibit the action of C'1 esterase, a plasma kallikrein, and PF/Dil, an enzyme in plasma enhancing cutaneous vascular permeability. In the present study, C'1 esterase inhibitor has been found to block the actions of plasmin and the C'1r subcomponent of the first component of complement, and to retard the generation of PF/Dil. No inhibition of blood clotting or of the generation of plasmin was demonstrable.

Alpha-Globulins↗
PubMed1978

Esterases in acute leukemias: a cytochemical and electrophoretic study.

Specific and nonspecific esterases were extracted from various typical cytologic types of leukemic blasts and subjected to electrophoresis in polyacrylamide gel. Preparations rich in normal granulocytes and normal monocytes were analyzed in a similar manner. The results indicated the presence of specific esterase activity in normal monocytes and in myelomonocytic and histiomonocytic leukemia, and a lack of consistent differences in the electrophoretic patterns of both specific and nonspecific esterases in these leukemias. The results support the viewpoint that distinctions between myelomonocytic and histiomonocytic leukemias cannot be made with certainty, and that they may represent variants within a broad spectrum of monocytic leukemias rather than separate and distinct entities.

Acute Disease↗
PubMed1979

Nonspecific esterases in leukemic blasts. Characterization by isoelectric focusing in polyacrylamide gel.

Using high-resolution technics of isoelectric focusing in polyacrylamide gel, isoenzymatic components of nonspecific esterases extracted from various cytologic types of leukemic blasts were visualized using alpha-naphthyl acetate and alpha-naphthyl butyrate as substrates. For each cytologic type of leukemic blast, consistent and distinctive patterns of nonspecific esterase activity were visualized. These studies provide further evidence for heterogeneity of nonspecific esterases, and for elaboration of isoenzymatic components as a reflection of cellular differentiation.

Esterases↗
PubMed1979

Studies of esterase-6 in Drosophila melanogaster. II. The genetics and frequency distributions of naturally occurring variants studied by electrophoretic and heat stability criteria.

Measurements of the electrophoretic mobility and thermostability of esterase-6 allozymes have been used to determine the amount of allelic variation at the esterase-6 locus in Drosophila melanogaster. We studied 398 homozygous lines obtained from four natural populations. Use of a spectrophotometric assay for esterase-6 activity has allowed precise quantitation of heat-stability variants. Using these methods, eight putative alleles were detected within the two most common electrophoretic classes. Analyses of F1 and F2 progeny show that the behavior of stability variants is consistent with the hypothesis that this variation is due to allelic variation at the Est-6 locus. Analyses of the gene-frequency distributions within and between populations show (1) that observed allele-frequency distributions do not deviate significantly from those expected for neutral variants, and (2) that there is little evidence for an increase in apparent divergence of the different populations at the genotypic or phenotypic levels when the additional variation detected is considered. These findings suggest that gene-frequency analysis alone is unlikely to resolve the question of the selective significance of allozyme variation.

Alleles↗