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PubMed2006

Effect of dietary conjugated linoleic acid and monounsaturated fatty acid content on pig muscle and adipose tissue lipase and esterase activity.

Three levels (0%, 1%, and 2%) of conjugated linoleic acid (CLA) were combined with two levels (low and high) of monounsaturated fatty acids (MUFA) for pig feeding. The activity of neutral lipase (NL), acid lipase (AL), phospholipase (PL), neutral esterase (NE), and acid esterase (AE) was measured in extracts from muscle and subcutaneous adipose tissues. The addition of CLA in the diet only affected the lipolytic activity in muscle, whereas differences in MUFA content of pig diets were mainly responsible for the lipolytic enzyme modifications observed in adipose tissue. Nevertheless, a significant effect of the interaction CLA x MUFA on the activity of several lipolytic enzymes was observed in both tissues. The effect of either linoleic acid (LA) or CLA on the activity of muscle and adipose lipolytic enzymes was determined by in vitro assays. Remarkable inhibitory or activation effects were detected depending on the enzyme and kind of tissue.

Adipose Tissue↗
PubMed1995

Esters of 3-pyridylacetic acid that combine potent inhibition of 17 alpha-hydroxylase/C17,20-lyase (cytochrome P45017 alpha) with resistance to esterase hydrolysis.

Esters of 3- and 4-pyridylacetic acid have been prepared and tested for inhibitory activity toward the human testicular 17 alpha-hydroxylase/C17,20-lyase and human placental aromatase enzymes. The structural features required for optimal inhibition of the hydroxylase/lyase enzyme were a 3-pyridine ring, methyl substitution alpha to the carbonyl group, and a bulky alkoxycarbonyl substituent. The compounds with the greatest selectivity were isopinocampheyl 2-methyl-2-(3-pyridyl)propanoate, 9, 1-adamantyl 2-methyl-2-(3-pyridyl)propanoate, 12, and 2-methyl-2-adamantyl 2-methyl-2-(3-pyridyl)propanoate, 14, which, while inhibiting the aromatase activity with IC50 values of 30, 35, and 40 microM, respectively, exhibited IC50 values toward hydroxylase/lyase of between 13 and 90 nM. For comparison, ketoconazole gave an IC50 value of 15 microM against aromatase and values of 65 and 26 nM for inhibition of the hydroxylase and lyase activities, respectively. Some of the structural features required for enzyme inhibition also conferred resistance to esterase hydrolysis, in vitro using rat liver microsomes as a source of the esterase activity. Therefore these esters are lead compounds in the development of inhibitors of androgen biosynthesis for the treatment of hormone-dependent prostatic cancer.

Adamantane↗
PubMed2001

Activation of pig liver esterase in organic media with organic polymers: application to the enantioselective acylation of racemic functionalized secondary alcohols.

Pig liver esterase (PLE) shows practically no activity in acylation of alcohols with vinylic esters in organic solvents. However, addition of methoxypoly(ethylene glycol) (MPEG), bovine serum albumin (BSA), TentaGelAmino resin (TGA), or aminomethyl polystyrene (AMPS) confers activity to PLE in acylation of alcohols with vinyl propionate in organic solvents of low water content. Polymer-activated PLE showed high enantioselectivities (E > 100) in the acylation of racemic 1-alkoxy-, 1-ethylsulfanyl-, and 1-fluoro-3-aryl-2-propanols as well as racemic 1-phenoxy-2-propanol and racemic 1-methoxy-2-phenoxy-2-propanol. The synthetic utility of polymer-activated PLE has been demonstrated by the gram-scale resolution of 1-methoxy-3-phenyl-2-propanol, 1-ethylsulfanyl-3-phenyl-2-propanol, 1-methoxy-3-p-methoxyphenyl-2-propanol, 1-fluoro-3-phenyl-2-propanol, and 1-methoxy-3-phenoxy-2-propanol. In PLE-catalyzed acylation of alcohols with vinyl propionate, acetaldehyde and propionic acids, both being detrimental to the enzyme, are formed as byproducts. In addition, the water content of the system, which is critical for the activity of pig liver esterase, is lowered because of a competing enzymatic hydrolysis of the acyl donor. The polymers TGA, BSA, and AMPS not only scavenge the aldehyde and the acid through imine formation and neutralization, respectively, but replenish at least in part also the water consumed in the competing hydrolysis of the acyl donor. A recovery of PLE together with the polymer was achieved without major loss of activity through their immobilization on a water-saturated polyaramide membrane, which occurs spontaneously in organic solvents.

Acylation↗
PubMed2001

Probing the active sites of butyrylcholinesterase and cholesterol esterase with isomalathion: conserved stereoselective inactivation of serine hydrolases structurally related to acetylcholinesterase.

Previous work has shown that acetylcholinesterase (AChE), a member of the alpha/beta-hydrolase superfamily, is stereoselectively inhibited by the four stereoisomers of isomalathion. Recent kinetic and mass spectral data demonstrated that a difference in mechanism of inactivation exists for AChE treated with (1R)- versus (1S,3S)-stereoisomers. This study sought to determine whether other alpha/beta-hydrolases are stereoselectively inhibited by isomalathion and if the difference in mechanism of AChE inactivation between (1R)- and (1S,3S)-isomers is conserved for other alpha/beta-hydrolases. Bimolecular rate constants of inhibition (k(i)) were measured for human and equine butyrylcholinesterase (HBChE and EBChE, respectively) and bovine cholesterol esterase (BCholE) with all four isomers. Isomalathion isomers inhibited these enzymes with the following order of potency: (1R,3R) > (1R,3S) > (1S,3R) > or = (1S,3S). Ratios of k(i) values for the most potent to the least potent isomer were 10.5 (HBChE), 11.9 (EBChE), and 68.6 (BCholE). Rate constants of reactivation (k(3)) were measured for enzyme inhibited by isomalathion isomers. HBChE, EBChE, and BCholE inactivated by the (1R)-isomers readily reactivated. However, enzymes modified by (1S)-isomalathions were refractory toward reactivation, and k(3) values were not significantly different from zero for HBChE and BCholE treated with the (1S,3S)-isomer. Computer-based docking experiments were performed for BCholE with (1R,3R)- and (1S,3S)-enantiomers. Calculated structures predicted a difference in primary leaving group: diethyl thiosuccinate for (1R,3R)-isomalathion and thiomethyl for the (1S,3S)-isomer. The data demonstrate that the alpha/beta-hydrolases used in this study are stereoselectively inhibited by isomalathion. Furthermore, the results suggest that the mechanistic shift demonstrated to occur for inhibition of AChE by (1R)- versus (1S,3S)-isomers is conserved for butyrylcholinesterase and cholesterol esterase.

Acetylcholinesterase↗
PubMed1999

Lack of effect of cholesterol esterase inhibitor CVT-1 on cholesterol absorption and LDL cholesterol in humans.

Two clinical trials were performed to test the hypothesis that CVT-1, a potent inhibitor of pancreatic cholesterol esterase, reduces percent cholesterol absorption and LDL cholesterol in humans. Measurements of cholesterol absorption were made with deuterated cholesterol tracers given orally and intravenously and detected in plasma by a new technique using negative ion mass spectrometry. Study 1 was a randomized, double-blind parallel study of CVT-1 treatment at doses of 0, 300, 1500, and 3000 mg/day in 19 subjects. Percent cholesterol absorption measured at baseline and again after 2 and 6 weeks showed no treatment effect and LDL cholesterol was unchanged. Study II was a randomized open-label crossover comparison between CVT-1 given as 1000 mg three times daily for 2 weeks and 187.5 mg hourly 16 hours/day for 2 weeks. Percent cholesterol absorption and plasma LDL cholesterol were not different between periods. We conclude that cholesterol esterase is not required for unesterified cholesterol absorption in human subjects.

Cellulose↗
PubMed1997

Esterase-sensitive cyclic prodrugs of peptides: evaluation of a phenylpropionic acid promoiety in a model hexapeptide.

PURPOSE: To evaluate a cyclic phenylpropionic acid prodrug of a model hexapeptide (H-Trp-Ala-Gly-Gly-Asp-Ala-OH) as a novel approach to enhance the membrane permeation of a peptide and stabilize it to metabolism. METHODS: Conversion to the linear hexapeptide was studied at 37 degrees C in HBSS, pH 7.4, and in various biological milieus having measurable esterase activities. Transport and metabolism characteristics were assessed using the Caco-2 cell culture model. RESULTS: In aqueous buffered solution, pH 7.4, the cyclic prodrug degraded quantitatively (t1/2 = 1795 +/- 289 min) to the linear hexapeptide and the lactone. Substantially faster degradation of the cyclic prodrug was observed in 90% human plasma (t1/2 = 508 +/- 24 min), and in homogenates of Caco-2 cells (t1/2 = 940 +/- 13 min), the rat intestinal mucosa (t1/2 = 1286 +/- 32 min), and rat liver (t1/2 = 840 +/- 42 min). Pretreatment of these biological media with paraoxon significantly decreased the degradation rate of the prodrug. When applied to the apical side of Caco-2 cell monolayers, the cyclic prodrug was significantly more stable than the hexapeptide and at least 71-fold more able to permeate (P(app) = 1.21 +/- 0.12 X 10(-7) cm/s) than was the parent peptide (P(app) < or = 0.17 x 10(-8) cm/s). In the presence of 0.1 mM palmitoyl-DL-carnitine, the transport rate of the cyclic prodrug (P(app) = 2.19 X 10(-6) cm/s) was 1250-fold greater than that of the linear hexapeptide. CONCLUSIONS: Preparation of a cyclic peptide using a phenylpropionic acid promoiety reduced the lability of the peptide to peptidase metabolism and substantially increased its permeation through biological membranes. In various biological media the parent peptide was released from the prodrug by an apparent esterase-catalyzed reaction, sensitive to paraoxon inhibition.

Animals↗
PubMed1996

Esterase-sensitive cyclic prodrugs of peptides: evaluation of an acyloxyalkoxy promoiety in a model hexapeptide.

PURPOSE: To evaluate a cyclic acyloxyalkoxycarbamate prodrug of a model hexapeptide (H-Trp-Ala-Gly-Gly-Asp-Ala-OH) as a novel approach to enhance the membrane permeation of the peptide and stabilize it to metabolism. METHODS: Conversion to the linear hexapeptide was studied at 37 degrees C in aqueous buffered solutions and in various biological milieus having measurable esterase activities. Transport and metabolism characteristics were assessed using the Caco-2 cell culture model. RESULTS: In buffered solutions the cyclic prodrug degraded chemically to the linear hexapeptide in stoichiometric amounts. Maximum stability was observed between pH 3-4. In 90% human plasma (t1/2 = 100 +/- 4 min) and in homogenates of the rat intestinal mucosa (t1/2 = 136 +/- 4 min) and rat liver (t1/2 = 65 +/- 3 min), the cyclic prodrug disappeared faster than in buffered solution, pH 7.4 (t1/2 = 206 +/- 11 min). Pretreatment of these media with paraoxon significantly decreased the degradation rate of the prodrug. When applied to the apical side of Caco-2 cell monolayers, the cyclic prodrug (t1/2 = 282 +/- 25 min) was significantly more stable than the hexapeptide (t1/2 = 14 min) and at least 76-fold more able to permeate (Papp = 1.30 +/- 0.15 x 10(-7) cm/s) than the parent peptide (Papp < or = 0.17 x 10(-8) cm/s). CONCLUSIONS: Preparation of a cyclic peptide using an acyloxyalkoxy promoiety reduced the lability of the peptide to peptidase metabolism and substantially increased its permeation through biological membranes. In various biological media the parent peptide was released from the prodrug by an apparent esterase-catalyzed reaction, sensitive to paraoxon inhibition.

Animals↗
PubMed1997

Isolation and characterization of an unamplified esterase B3 gene from malathion-resistant Culex tarsalis.

A malathion-resistant strain of Culex tarsalis has a malathion carboxylesterase which rapidly hydrolyzes the insecticide. This is in contrast to organophosphate-resistant strains of C. quinquefasciatus and C. pipiens, which have elevated levels of general B esterases due to amplification of the corresponding genes, producing increased amounts of enzyme which appear to protect the insects by sequestering the insecticide. The contribution to resistance of the homologous esterase B3 (Est beta 3) gene (est beta 3) in C. tarsalis was investigated by cloning and characterizing sequences from resistant and susceptible strains. est beta 3 is similar to est beta 1, both structurally and in sequence. The first intron of est beta 3, however, has a region of extensive repeats which may be responsible for the inefficient processing of the transcript. Southern blots indicate that the gene is single copy in both strains, and northern blots show that it is not greatly overexpressed in the resistant insects. est beta 3 cDNAs from resistant and susceptible strains have 98% amino acid identity. It appears that, in contrast to other studies, est beta 3 does not play a significant role in insecticide resistance in our strains of C. tarsalis, and the molecular responses of pest insects to organophosphates may be more diverse than has been suggested.

Amino Acid Sequence↗
PubMed2004

Application of glutaraldehyde for the staining of esterase-active cells with carboxyfluorescein diacetate.

Staining of esterase-active bacteria with carboxyfluorescein diacetate (CFDA) has been used to evaluate the viability of various types of cell. However, the outer membrane of Gram-negative bacteria prevents CFDA from permeating into the cell. Although EDTA can increase the permeability of the outer membrane allowing CFDA to enter the cells, it was experimentally confirmed that there is still considerable difficulty in visualizing viable cells due to passive diffusion of carboxyfluorescein (CF), a hydrolyzed product of CFDA, out of the cells. We found that glutaraldehyde enhances the discriminative recognition of esterase-active Gram-negative bacteria under microscopic observation by improving the efficacy of staining. We believe the successful staining in the presence of glutaraldehyde is due to two separate effects: an increase in the permeability of CFDA into the cell and prevention of leakage of CF out of the cell.

Cell Membrane Permeability↗
PubMed1975

Food induced esterase phenocopies in the snail Cepaea nemoralis.

Hepatopancreatic extracts from the snail Cepaea nemoralis, assayed straight from the field, often contain three or four heavily staining esterase zones which migrate to the cathodal end of polyacrylamide disc gels during electrophoresis. Previous breeding results showed that the heavily straining zones appeared allelic but to incorporate these multibanded phenotypes, a super gene of five closely linked loci was tentatively proposed. Further breeding work again failed to demonstrate multiple zones in parents or offspring and so experiments were conducted to see whether the multi-zoned phenotypes in the wild were produced by secondary modification of single primary products. Wild snails yielding extracts containing more than two heavily staining zones were shown to possess only two such zones after three months under laboratory conditions. Also, the ingestion of nettle (Urtica dioica L.) has been demonstrated to induce extra esterase zones in laboratory-reared animals. Some of the secondarily induced zones appear identical in physical, biochemical and electrophoretic properties to the primary products of other alleles, and thus appear to be electrophoretic phenocopies. A model is suggested which could account for this phenomenon.

Aneuploidy↗
PubMed1988

Phenotypic variability and heterozygosity at an esterase locus in the mosquito Aedes aegypti.

Populations of the yellow fever mosquito, Aedes aegypti L. are polymorphic for esterase alleles. This could be because the alleles are neutral or because selection protects the polymorphism, as had been concluded from a study of allele frequencies. A test has been carried out to look for possible associations of esterase heterozygosity with speed of development, body size and spine number symmetry in two spine rows. Heterozygotes were found to be larger and slower growing than homozygotes, but there was no difference in degree of asymmetry. There were fewer heterozygotes and a greater deficiency compared with expectation in insects reared at higher temperatures. It is concluded that different genotypes do differ in fitness.

Aedes↗
PubMed2006

Low background FRET-substrates for lipases and esterases suitable for high-throughput screening under basic (pH 11) conditions.

FRET-based fluorogenic substrates for lipases and esterases were prepared in four steps from commercially available building blocks. The substrates are pyrenebutyric acid monoesters of aliphatic 1,2-diols bearing a dinitrophenylamino group as a quencher. The most enzyme-reactive substrate is ester 2a. The substrates do not show any measurable background reaction in the absence of enzyme even at pH 11, but react fast and specifically with lipases and esterases. These substrates offer an unprecedented and practical solution to the long-standing problem of a simple yet efficient high-throughput screening tool for lipase activities under basic conditions.

Dinitrobenzenes↗
PubMed1966

The esterase and depsidase activities of tannase.

The esterase and depsidase activities of tannase have been examined by kinetic methods. Although the esterase/depsidase ratio of tannase may be varied by cultural methods and isolation procedures, evidence has been obtained to show that tannase, esterase and depsidase are enzymes with low specificities capable of hydrolysing both esters and depsides of gallic acid.

Chemical Phenomena↗
PubMed1979

Rapid aging of neurotoxic esterase after inhibition by di-isopropyl phosphorofluoridate.

1. It was proposed [Johnson (1974) J. Neurochem.23, 785-789] that an essential step in the genesis of delayed neuropathy caused by some organophosphorus esters was aging of phosphorylated neurotoxic esterase, involving generation of a charged monosubstituted phosphoric acid residue on the protein. 2. Neurotoxic esterase of hen brain was inhibited with di-isopropyl phosphorofluoridate either unlabelled or mixed-labelled with (3)H and (32)P. 3. Reactivation of inhibited enzyme by KF was possible only immediately after a brief inhibition:aging at pH8.0 and 37 degrees C occurred with a half-life of about 2-4min. 4. When the radiolabelled enzyme was studied no loss of label was observed during the expected aging period, but a change in the nature of the bound radioisotopes occurred (half-life=3.25min). 5. Alkaline hydrolysis of labelled enzyme liberated di-isopropyl phosphate at early times after labelling, but increasing amounts of monoisopropyl phosphate plus a volatile tritiated compound (possibly propan-2-ol) at later times. 6. Treatment of labelled enzyme with KF released di-isopropyl phosphate and caused reactivation of enzyme to similar degrees. It is concluded that the chemical change from di-isopropyl phosphoryl-enzyme to mono-isopropyl phosphoryl-enzyme and the loss of reactivatibility are related. 7. The rate of aging is similar at pH5.2, 6.5 and 8. Aging is unaffected by addition of reduced glutathione and imidazole at pH5.2 or 8, and none of the transferred (3)H is trapped by these reagents. The mechanism of aging must be different from the better-known dealkylation aging of the cholinesterases.

Animals↗
PubMed2002

Denaturing action of urea and guanidine hydrochloride towards two thermophilic esterases.

The stability of two thermophilic esterases, AFEST from Archaeoglobus fulgidus and EST2 from Alicyclobacillus acidocaldarius, against the denaturing action of urea and guanidine hydrochloride has been investigated by means of steady-state fluorescence and circular dichroism measurements. Experimental results indicate that the two enzymes, even though very resistant to temperature and urea, show a resistance to guanidine hydrochloride weaker than expected on the basis of data collected so far for a large set of globular proteins. Structural information available for AFEST and EST2 and ideas that emerged from studies on the molecular origin of the greater thermal stability of thermophiles allow the suggestion of a reliable rationale. The present results may be an indication that the optimization of charge-charge interactions on the protein surface is a key factor for the stability of the two esterases.

Archaeoglobus↗
PubMed1998

Evidence that the E4 and FE4 esterase genes responsible for insecticide resistance in the aphid Myzus persicae (Sulzer) are part of a gene family.

The amplification of genes encoding the esterases E4 and FE4 is a widespread mechanism of insecticide resistance in the peach-potato aphid, Myzus persicae (Sulzer). We present evidence that in susceptible aphids the two genes are adjacent to each other in a head-to-tail arrangement with E4 upstream of FE4 and with approx. 19 kb of intervening sequence. There are also at least two other closely related sequences which might come from other members of an esterase gene family, in line with reports of other insect gene families encoding detoxifying enzymes. The close identity between E4 and FE4 genes indicates a recent duplication and divergence. The subsequent amplifications giving multiple copies of either E4 or FE4 must have involved two separate events, each probably occurring once and then being selected by insecticide exposure and spread by migration. The cloning of sequences upstream of the FE4 gene suggest, by comparison with E4, that the two genes are regulated in different ways. FE4 has sequences corresponding to a conventional promoter (TATA box and CAP site) that are not present in E4; on the other hand, FE4 lacks the CpG island present 5' of E4 genes that may control expression through changes in DNA methylation. The differences are likely to have occurred by the duplication event that gave rise to E4 and FE4 leading to different 5' sequences.

Animals↗
PubMed1999

Double esterase staining of the bone marrow contributes to lineage identification in a case of minimally differentiated acute myeloid leukaemia (AML M0).

Minimally differentiated acute myeloid leukaemia (AML-M0) may pose difficulty in diagnosis since morphological criteria alone are not reliable. Other studies such as electron microscopy, immunocytochemistry and surface marker analysis are needed. The role of cytochemistry has been limited to the negative staining of blasts for Sudan Black B and myeloperoxidase. An abnormal morphology and cytochemistry of bone marrow maturing cells may indicate the myeloid nature of acute leukaemia. In this case of AML-M0, increased numbers of maturing and mature bone marrow granulocytic cells staining simultaneously for both specific and non-specific esterase (double esterase) are described. In acute leukaemia, this abnormal cytochemical finding seems to be specific for myeloid leukaemia and may be used as supplementary evidence of myeloid differentiation of morphologically undifferentiated blasts in cases of AML-M0.

Acute Disease↗