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PubMed1986

Isolation and characterization of a serine esterase from cytolytic T cell granules.

Cytotoxic T lymphocytes and lymphocytes with NK-like activity contain a serine esterase activity which has been localized to their cytoplasmic granules by cytochemistry and subcellular fractionation studies. The serine esterase-specific inhibitor 3H-DFP labels two protein species in the granules. The two proteins, referred to as serine esterases 1 and 2 (SE 1 and SE 2), migrate with Mr of 34-36 kd and 28-30 kd, respectively, under reducing conditions. SE 1 shows trypsin-like activity and has been purified to apparent homogeneity. Under nonreducing conditions, SE 1 has an Mr of 60-66 kd, suggesting that it may consist of two disulfide-linked subunits of 34-36 kd each. SE 1 cleaves fibrin and casein, has a pl greater than 10, and optimal activity at pH 8. The substrate specificity of SE 2 is not known. The serine esterase activity is secreted by lymphocytes that have been stimulated with the calcium ionophore A23187. The serine esterases described here could play an active role in cell-mediated killing.

Animals↗
PubMed1993

Esterases of xylan-degrading microorganisms: production, properties, and significance.

This review focuses on the description of recently discovered esterase enzymes involved in xylan degradation (acetyl xylan, feruloyl, and p-coumaroyl esterases). The occurrence of these enzymes in various microorganisms, assays used for determination of their activity, induction and production on different substrates, interaction with other xylanolytic enzymes, mode of action, substrate specificity, and biochemical characteristics are presented. The nature of substrates on which acetyl xylan esterase, feruloyl, and p-coumaroyl esterase are active and their role in xylan hydrolysis is emphasized. The potential applications of xylan-debranching esterases are outlined and their significance to applied microbiology is discussed.

Acetylesterase↗
PubMed1988

The esterase-like activity of covalently bound human third complement protein.

The acyl ester bond between the third complement protein, C3, and a variety of molecules is hydrolyzed spontaneously at neutral pH (Venkatesh et al., 1984). Modification of the free, single sulfhydryl group of bound C3 by thiol reagents suggested that a functional group other than the -SH acts as a "catalytic" group in this intramolecular hydrolytic reaction. Complete inhibition of the esterase-like activity is observed with stoichiometric amounts of mercuric chloride, palladium chloride, and the bifunctional organic mercurial, 3,6-bis-(acetoxymercuri)-o-toluidine [BAMT]. Since alkyl and aryl mercuric ions do not inhibit the esterase-like activity of C3-[3H]glycerol, it is conjectured that divalent mercury, palladium, and BAMT will form a complex with the -SH group and an atom of the "catalytic" group X having a lone pair of electrons. The structural features of C3 that are essential for the esterase-like activity remain intact after subjecting C3-[3H]glycerol to covalent chromatography on organomercurial agarose. Based on the observed effects of chemical reagents and the kinetic deuterium solvent isotope effect on the esterase-like activity, a general-base mechanism is proposed for the intramolecular hydrolysis of the acyl ester bond in covalently bound C3. The "catalytic" group X is located in the C3d region (residues 317-632 of the alpha chain), since C3d-[3H]glycerol also has esterase-like activity. A general-base mechanism mediated by the same "catalytic" group X may also apply to the formation of acyl ester bonds following the hydrolysis of the internal thiolester bond in native C3.

Chemical Phenomena↗
PubMed1979

Esterase-7, a common constituent of numerous mouse tissues.

1. Electrophoretic and staining techniques for the relatively specific demonstration of esterase-7 in mouse tissues are described. Esterase-7 was found to be a common constituent of most mouse tissues. 2. The electrophoretic polymorphisms determined by three alleles a, b and c were studied in nine mouse strains. 3. The banding pattern of esterase-7 is being described and the isoelectric points of the allelic bands are being estimated. 4. Recombination studies on a further 129 animals confirmed that the Es-7 locus is tightly linked to Es-2 and Es-11. 5. Esterase-7 precipitates with antiesterase-2 from the rabbit. 6. It differs from esterase-2 by its individual substrate preference and by its susceptibility to inhibition by acylating agents.

Alleles↗
PubMed1988

Physicochemical characterization and tissue distribution of multiple molecular forms of fish (Trachurus trachurus) esterases.

1. Tissue-specific electrophoretic patterns of multiple molecular forms of esterases were observed in fish Trachurus trachurus. They were composed of three (in intestine) to nine (in liver) bands characterized mainly as carboxylesterases and acetylesterases. 2. Two major esterase activity bands of pI 4.60 and 4.77 were accompanied by minor ones of higher pH in tissue extracts. 3. Under optimum assay conditions, liver was the richest source of esterase activity followed by intestine, stomach, brain, red muscles, heart, white muscles and gills. 4. Esterases of 70,000 and 420,000 mol. wt were resolved by gel-filtration in liver, intestine and brain. Low size esterases prevailed in liver while the opposite was the case in brain.

Animals↗
PubMed2005

Acidic residues emulate a phosphorylation switch to enhance the activity of rat hepatic neutral cytosolic cholesterol esterase.

Site-directed mutagenesis of rat hepatic neutral cytosolic cholesteryl ester hydrolase (rhncCEH) was used to substitute acidic, basic or neutral amino acid residues for Ser506, required for activation by protein kinase A. The substitution of acidic Asp506 resulted in esterase activities with cholesteryl oleate, p-nitrophenylcaprylate (PNPC) and p-nitrophenylacetate (PNPA) equivalent to those of native rhncCEH with Ser506. The substitution of 2 acidic residues (Asp505/506), emulating the 2 negative charges of phosphoserine, resulted in a 10-fold greater cholesterol esterase activity than that of native rhncCEH, similar to the activity of rhncCEH treated with protein kinase A. In contrast to mutants with Ser506, protein kinase A did not increase the specific activities of mutants with Asp505/506. The substitution of basic (Lys506) or neutral (Asn506) residues abolished activity with cholesteryl oleate but not PNPC or PNPA. The substitution of neutral Gln for basic residues Lys496/Arg503 also abolished cholesterol esterase activity but not PNPC- and PNPA-esterase activities. These structure-activity relationships are modeled by homology with a recently reported crystal structure for the homologous human triacylglycerol hydrolase. The results suggest that the cholesterol esterase activity of carboxylesterases is enhanced by interactions between one or more basic residues on helix alpha16 (residues 485-503) and acidic groups at residues 505-506 in the adjacent surface loop.

Amino Acid Sequence↗
PubMed2004

Simultaneous analysis of esterase and transferase activities in cytosol proteins from the bovine retina by using microscale non-denaturing two-dimensional electrophoresis.

Esterase and transferase activities were analyzed simultaneously after cytosol proteins in the bovine retina were separated by microscale non-denaturing two-dimensional electrophoresis (2-DE). Esterase activity was specifically inhibited by an esterase inhibitor, 9-amino-1,2,3,4-tetra hydroacridine (tacrine), and transferase activity was specifically inhibited by a glutathione S-transferase (GST) inhibitor, 2-phenyl-1,2-benziso selenazol-3(2H)-one (ebselen). Both esterase and transferase were precipitated when ammonium sulfate was added to the cytosol up to 50% saturation (50% AS fraction), and were detected in the 50% AS fraction by using the 2-DE. After the cytosol proteins in the 50% AS fraction were separated by using non-denaturing 2-DE, polypeptides of the separated proteins were identified by peptide mass fingerprinting and post-source decay analysis by using MALDI-MS, or by immunoreactivity by using a specific antibody. The spots of esterase and transferase activities in the 2-DE pattern were identified as phosphodiesterase and GST, respectively. This simultaneous analysis of enzyme activities can be applied to screen-specific or non-specific medicines which affect enzyme activities.

Animals↗
PubMed2003

Evaluation of alpha-cyanoesters as fluorescent substrates for examining interindividual variation in general and pyrethroid-selective esterases in human liver microsomes.

Carboxylesterases hydrolyze many pharmaceuticals and agrochemicals and have broad substrate selectivity, requiring a suite of substrates to measure hydrolytic profiles. To develop new esterase substrates, a series of alpha-cyanoesters that yield fluorescent products upon hydrolysis was evaluated for use in carboxylesterase assays. The use of these substrates as surrogates for Type II pyrethroid hydrolysis was tested. The results suggest that these novel analogs are appropriate for the development of high-throughput assays for pyrethroid hydrolase activity. A set of human liver microsomes was then used to determine the ability of these substrates to report esterase activity across a small population. Results were compared against standard esterase substrates. A number of the esterase substrates showed correlations, demonstrating the broad substrate selectivity of these enzymes. However, for several of the substrates, no correlations in hydrolysis rates were observed, suggesting that multiple carboxylesterase isozymes are responsible for the array of substrate hydrolytic activity. These new substrates were then compared against alpha-naphthyl acetate and 4-methylumbelliferyl acetate for their ability to detect hydrolytic activity in both one- and two-dimensional native electrophoresis gels. Cyano-2-naphthylmethyl butanoate was found to visualize more activity than either commercial substrate. These applications demonstrate the utility of these new substrates as both general and pyrethroid-selective reporters of esterase activity.

Aldehydes↗
PubMed1997

Stereospecific activity and nature of metabolizing esterases for propranolol prodrug in hairless mouse skin, liver and plasma.

Cutaneous stereoselective hydrolyses of ten ester prodrugs of propranolol in hairless mouse were compared to those in liver and plasma. On the basis of protein content, the hydrolysis rate was greatest with liver homogenate followed by plasma and skin homogenate. The buffer showed the slowest and non-stereoselective hydrolysis. However, skin showed very high stereoselectivity (R/S ratio: 6.7-18.4) as compared with liver (0.7-2.0) and plasma (1.7-4.7). The microsomal esterase activity was higher than cytosolic esterase in liver, while an opposite relation was observed in skin. The smaller Km and larger Vmax values of the (R) isomer than those of the (S) isomer of caproyl- and/or butyryl-propranolol were found in skin and plasma, while Km was the same between (R) and (S) isomers in liver. Enzyme inhibition studies indicated that the carboxylesterases were primarily involved in prodrug hydrolysis in liver. On the other hand, skin and plasma were found to be rich in both carboxylesterases and cholinesterases. Interestingly, the (R) isomer was more sensitive towards butylcholinesterase in skin and plasma, while (S) isomer was more sensitive towards carboxylesterase in plasma. Moreover, no stereoselective inhibition was observed in liver. These data indicated that the hydrolyzing nature of skin esterases responsible for propranolol prodrug was sensitive against stereochemical configuration and more similar to those in plasma esterases than liver esterases.

Adrenergic beta-Antagonists↗
PubMed1976

[A contribution of the histochemical behaviour of the unspecific esterases in hypothalamus, neurohypophysis, adrenal and parotid gland of the rat against inhibitors].

On continuation of study by KURZ and GOSLAR (1974) concerning the inhibitory effects to non specific esterases on liver and kidney, the behaviour of alpha-naphthyl-acetate-esterases on hypothalamus, neurohypophysis, adrenal and parotid glands of rats had been examined against aldehydes, organic solution-mediators and anorganic salts. It had shown a different sensitiveness, the esterases of tanycytes, nerve cells and pituicytes acted more sensitive than those of the adrenal cortex and parotid gland. The differences seen on the solution-mediators were less; on metal salts from different groups of periodical system which applied, the most intense blocking effect was found in the nerve cells. The esterases of tanycytes and the immediately extensively reacting pituicytes, as well as the adrenal cortex esterases reacted essentially less sensitive, the gland cells of parotid even almost not at all. The arguments of this behaviour are discussed and pointed out with different complexity of alpha-naphthylacetate splitting enzymes on individual organs.

Adrenal Cortex↗
PubMed1978

Studies on the oxidizing system in Holt's medium for histochemical demonstration of esterase activity.

Esterase activity in guinea-pig thyroid and mouse epididymis epithelial cells has been studied using 5-bromoindoxyl acetate as substrate. The pattern of esterase activity in the thyroid of the guinea-pig is constant, irrespective of whether ferri-ferrocyanide (FFC) or certain copper compounds are used as oxidizing agents in the incubation medium. The intensity of the coloured reaction product is increased when cobalt or manganese are added to the incubation medium. Activity is depressed by high concentrations of FFC when resent in incubation medium or preincubational buffer only. Epididymis cells contain an esterase activity which is not inhibited by conventional SH blocking agents, nor by high concentrations of FFC. From these results it appears that the mode of action of FFC in Holt's medium is as follows. At low concentrations FFC appears to act primarily as a catalytic agent in oxidation of indoxyl to indigoid. At high concentration FFC acts as an inhibitor of guinea-pig thyroid esterase, by oxidation of SH groups in the active centre. The esterase of mouse epididymis cell type EH 1 is not subject to this inhibition by FFC, presumably because it does not contain accessible SH groups in the active centre.

Animals↗
PubMed1979

Localization of non-specific esterase and acid phosphatase in human fibroblast from skeletal muscle atrophy.

The intracellular localization of non-specific esterase and acid phosphatase was investigated in human fibroblast cells from skeletal muscle atrophy. Non-specific esterase and acid phosphatase positive sites were visualized ultrastructurally in the fibroblast. Electron microscopy for the cytochemistry of these enzyme was performed in human atrophic skeletal muscle by using thiol acetate esterase method and GOMORI'S method. Lipofuscin pigment granules in fibroblast cells contain dense pigment, granular matrix and lipid droplet. Reaction products of non-specific esterase are seen in the pigment and granular matrix, and they may therefore be called residual bodies. Reaction products of acid phosphatase and non-specific esterase were found to be located in lysosomes.

Acid Phosphatase↗
PubMed1984

Measurement of urinary leukocyte esterase activity: a screening test for urinary tract infections.

We evaluated the efficacy of testing for the presence of esterase (an enzyme released only from leukocytes) in the urine as an indicator of the presence of pyuria. We hypothesized that a "dipstick" test for urinary leukocyte esterase activity would be a rapid and simple screening technique for detecting urinary tract infections (UTI). To test our hypothesis we collected fresh urine specimens from 203 patients (148 outpatients, 55 inpatients) with a suspected UTI. Each specimen was divided into three aliquots; one was used for reagent strip testing (for leukocyte esterase, nitrite, and blood), one for microscopy, and one for culture. Of the 203 specimens, 49 showed significant bacteriuria (greater than or equal to 10(5) organisms/mL). The leukocyte esterase test was 100% sensitive (0% false negatives) with a 76% specificity (24% false positives) in predicting significant bacteriuria. Although a positive nitrite reaction was more specific (99% specificity, 0.6% false positives), it was insensitive (27% sensitivity, 73% false negatives). The high sensitivity of reagent strip leukocyte esterase testing for pyuria makes it a valuable screening test that should lead to the elimination of many needless urine cultures and microscopic examinations.

Adult↗
PubMed2000

Differential glycosylation produces heterogeneity in elevated esterases associated with insecticide resistance in the brown planthopper Nilaparvata lugens Stål.

The major insecticide resistance mechanism in the brown planthopper Nilaparvata lugens involves overproduction of esterases. Esterases purified from a resistant strain appeared as a ladder of bands on isoelectric focussing (IEF) gels from pI 4.7 to 5.0. Two-dimensional electrophoresis showed that isozymes ranged in size from 66 to 68 kDa with those of lower pI being apparently smaller. All isozymes detected by two-dimensional electrophoresis were glycosylated. N-glycosidase A reduced the number of isozymes on IEF to two, with increased pI and an increased molecular weight of 69 kDa. No O-linked glycans were detected. Deglycosylation had no effect on esterase activity, hence glycosylation is not involved in active site conformation. As N-glycosidase F completely deglycosylated the esterases, none of the glycans has an alpha1,3-bound core fucose. Reactivity with the lectins GNA, MAA and DSA, combined with differential cleavage of N-linked glycans with endoglycosidases F1 and F2, indicated that terminally linked mannose is present in high mannose and/or hybrid type glycans and that terminally linked sialic acid and galactose-beta(1-4)-N-acetylglucosamine are present in biantennary complexes. Neuraminidase treatment had the same effect on pI of isozymes as complete deglycosylation. Therefore, the majority of the heterogeneity of elevated esterases on IEF is due to differential attachment of sialic acid to glycans of the two proteins.

Animals↗
PubMed2000

Cloning of a horn fly cDNA, HialphaE7, encoding an esterase whose transcript concentration is elevated in diazinon-resistant flies.

Reverse transcriptase-polymerase chain reaction (PCR) was used to clone two esterase cDNAs from a diazinon-resistant field population of horn flies that expresses qualitative and quantitative differences in esterases compared with a susceptible population. The open reading frame from one of the esterase cDNAs, HialphaE7, exhibits substantial amino-acid identity to an esterase associated with diazinon resistance in Lucilia cuprina. RNA Northern blots showed that HialphaE7 mRNA was more abundant in the diazinon-resistant population than the susceptible population. DNA copy number analysis did not reveal major differences in HialphaE7 gene copy number between the two populations. The full-length cDNA to HialphaE7 was cloned and sequenced, and found to contain all of the highly conserved sequence elements associated with carboxyl/cholinesterases. The HialphaE7 homologs in diazinon-resistant strains of L. cuprina and Musca domestica have been shown to possess an amino-acid substitution conferring diazinon hydrolytic activity to the esterase enzyme. This amino-acid substitution was not found in diazinon-resistant horn flies examined by allele-specific PCR. Individual flies from the resistant field population were phenotyped as diazinon-resistant or diazinon-susceptible by topical diazinon application bioassays and total RNA isolated and hybridized to HialphaE7 probe in ribonuclease protection assays. HialphaE7 transcript was expressed at a five-fold higher level in resistant female individual flies than in susceptible female individuals.

Amino Acid Sequence↗
PubMed1992

Purification of pancreatic cholesterol esterase expressed in recombinant baculovirus-infected Sf9 cells.

A cDNA clone encoding the entire coding sequence of rat pancreatic cholesterol esterase (bile salt-stimulated lipase) was subcloned into the Baculovirus transfer vector pVL1392 and used to co-transfect Spodoptera frugiperda (Sf9) insect cells with wild-type Autographa californica nuclear polyhedrosis virus (AcNPV) DNA. Two recombinant proteins (M(r) 74 kDa and 64 kDa) reactive with anti-cholesterol esterase IgG were produced and secreted by the infected Sf9 cells in large quantities in a time-dependent manner. The 74-kDa protein was detectable in the cultured medium at the second day post-infection and increased progressively, reaching a level of 50 micrograms/ml of culture medium after 8 days. Amino-terminal sequencing of this recombinant protein showed that the signal peptide of cholesterol esterase was correctly cleaved, resulting in the production of mature protein. The 64-kDa recombinant protein was not detected in the medium until Day 5 post-infection and accumulated to a level of 25 micrograms/ml at Day 8. Both the 74- and the 64-kDa cholesterol esterases were biologically active and hydrolyzed the artificial substrate p-nitrophenyl butyrate. Results of this study demonstrated that Baculovirus-infected Sf9 cells can be used for high-level expression of pancreatic cholesterol esterase. The recombinant enzyme will be useful for further characterization of this protein.

Animals↗
PubMed2000

Purification and characterization of an esterase conferring resistance to fenitrothion in Oryzaephilus surinamensis (L.) (insecta, coleoptera, silvanidae).

Esterases from a fenitrothion-resistant strain (VOSF) of the saw-toothed grain beetle, Oryzaephilus surinamensis (L.), are presumed to play a role in conferring resistance to malathion, fenitrothion, and chlorpyrifos-methyl. Colorimetric assays showed a significant positive correlation between increased resistance to fenitrothion in strains of O. surinamensis examined and elevated esterase hydrolytic activity to substrates of p-nitrophenyl acetate, alpha-naphthyl acetate, and beta-naphthyl acetate. Esterase zymograms showed different banding patterns between VOSF and an insecticide-susceptible strain, VOS48. A major esterase in the VOSF strain, not detected in VOS48, was purified and characterized by chromatographic and electrophoretic techniques. On the basis of SDS-polyacrylamide gel eletrophoresis, the molecular mass of the purified esterase from VOSF was 130 kDa and consisted of two 65 kDa subunits. Additional properties of this enzyme are discussed.

Animals↗
PubMed1999

3-Alkyl-6-chloro-2-pyrones: selective inhibitors of pancreatic cholesterol esterase.

A series of 3-alkyl-6-chloro-2-pyrones with cyclohexane rings tethered to the 3-position was synthesized. The tether ranged from 0 to 4 methylene units. Inhibition of pancreatic cholesterol esterase by this series of pyrones was markedly dependent upon the length of the tether. Dissociation constants as low as 25 nM were observed for 6-chloro-3-(1-ethyl-2-cyclohexyl)-2-pyranone. This class of cholesterol esterase inhibitors functioned as simple competitive inhibitors of substrate binding rather than as suicide substrates or active site inactivators. Trypsin and chymotrypsin were not strongly inhibited by this class of pyrones. Selectivities for cholesterol esterase were greater than 10(3). This is in contrast to 3-aryl-6-chloro-2-pyrones which are nonselective, irreversible inactivators of serine hydrolases. Thus, replacement of the 3-aryl group by an appropriately tethered 3-alkyl ring can produce highly selective inhibitors of cholesterol esterase. A second series of halogen-containing esters was prepared in which cholesterol was esterified with alpha-haloacyl halides. These haloesters were simple substrates of cholesterol esterase with no evidence of irreversible inactivation.

Cholesterol↗