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PubMedDate not supplied

Enantioselectivity of microsomal and cytosolic esterases in rat intestinal mucosa.

Enantioselectivity of esterases, contained in 9,000g supernatant fraction (S9) prepared from homogenate of small intestinal mucosa of male Sprague-Dawley rats and the subsequent 105,000g supernatant (cytosol) and pellet (microsomes) prepared from S9, was studied using racemic oxazepam 3-acetate (rac-OXA) as the substrate. Esterases in S9 were enantioselective in hydrolyzing either S-OXA or R-OXA, depending on a particular subcellular preparation. Cytosolic and microsomal esterases had opposite enantioselectivity and selectively hydrolyzed S-OXA and R-OXA, respectively. Enantioselectivity of esterases solubilized from microsomes with Triton X-100 (0.1%, w/v) was identical to that of the membrane-bound microsomal esterases. Cytosolic esterases were more sensitive to temperature than either solubilized or membrane-bound microsomal esterases. In the presence of paraoxon (1 microM), the esterases selective toward R-OXA in both microsomes and S9 were completely inhibited, whereas the esterases selective toward S-OXA in cytosol were inhibited by approximately 6%. These results indicate that cytosolic and microsomal esterases in rat small intestinal mucosa are distinctly different enzymes, with opposite enantioselectivity in the hydrolysis of rac-OXA.

Animals↗
PubMedDate not supplied

[An effect of the microsporidian Vairimorpha ephestiae (Microsporidia: Burenellidae) on activity and spectrum of nonspecific esterases in different tissues of the greater wax moth galleria mellonella (Lepidoptera: Pyralidae) larvae].

The effect of the microsporidian Vairimorpha ephestiae Matted (Microsporidia: Burenellidae) on nonspecific esterases was studied in hemolymph, fat body and midgut of the larvae of Galleria mellonella L. (Lepidoptera: Pyralidae). Esterase patterns were analyzed by the polyacrylamide gel electrophoresis, the total esterase activity was detected spectrophotometrically. The increase of total esterase activity was registered in hemolymph of inflected larvae. An overexpression of esterase isozyme in hemolymph was already detected at the 3rd day post infection. No changes in esterases pattern were observed in the fat body's homogenates of the G. mellonella larvae possessing the symptoms of microsporidiosis. The degradation of esterase isozymes and the decrease of total esterase activity in the pattern of the midgut homogenates of infected larvae were registered during parasite sporogony. The greatest esterase activity in hemolymph and midgut tissues was registered during vegetative reproduction of parasite, but the least level of esterase activity was observed during mass sporogony of microsporidia.

Animals↗
PubMed1991

Cholesterol esterase biosynthesis in rat pancreatic AR42J cells. Post-transcriptional activation by gastric hormones.

This study used the rat pancreatoma AR42J as a model system to investigate the possible regulation of cholesterol esterase biosynthesis in pancreas. Initial experiments were performed to verify the synthesis of pancreatic cholesterol esterase by the AR42J cells. Results indicated that this pancreatoma cell line synthesized two forms of cholesterol esterase (Mr = 71,000 and 74,000). The 74-kDa protein is most likely the precursor protein, and the 71-kDa protein is the matured enzyme secreted by the AR42J cells. The synthesis and secretion of cholesterol esterase were stimulated 2-5-fold by incubating the cells with 0.5-4 nM of cholecystokinin or 0.5-2 nM of secretin. Analysis of the RNA isolated from the hormone-stimulated cells revealed that stimulation of cholesterol esterase biosynthesis was not due to an increase in cholesterol esterase mRNA. Furthermore, inhibition of transcription with actinomycin D has no effect on the hormone-induced cholesterol esterase biosynthesis. Therefore, the mechanism of hormone stimulation was not dependent on de novo RNA synthesis. In vitro translation studies showed that the cholesterol esterase mRNA isolated from stimulated AR42J cells were translated more efficiently than those from control cells. Thus, the increased cholesterol esterase biosynthesis induced by gastric hormones was most likely mediated by posttranscriptional modification of the cholesterol esterase mRNA.

Animals↗
PubMed1977

Identification of human mononuclear leucocyte populations by esterase staining.

Histochemical staining for alpha-naphthyl (non-specific) esterase has been employed to define subpopulations of human peripheral blood lymphocytes and monocytes. To define optimal conditions for staining, various fixatives, incubation times and cell preparations were compared. The great majority of human blood lymphocytes were found to have discrete granules of reaction product. More than 80% of T lymphocytes separated by E rosetting are esterase-positive whereas non-T lymphocytes are esterase-negative. Lymphocytes transformed by polyclonal mitogens lose their esterase-staining granules, which suggests that immature T cells are esterase-negative. Most blood monocytes show a diffuse cytoplasmic esterase reaction product and are phagocytic. However, about 20% of diffusely stained cells are not phagocytic. When leucocytes are cultured for 24 to 48 hr, the total number of esterase-positive cells increases and the great majority are phagocytic. This is interpreted as maturation of precursors into mature esterase-positive phagocytic monocytes. When cultured for longer periods, some lose phagocytic capacity and acquire the characteristics of secretory cells. Esterase-staining of lymph node sections allowed the identification of T- and B-dependent areas as well as macrophages related to sinuses. The esterase-staining technique could play a useful role in clinical and experimental immunology.

Esterases↗
PubMed1998

Hydrophobilization of esterase by genetic combination with polyproline or polytyrosine at the carboxyl terminal.

Polyproline (Poly-Pro) that is an amphiphilic polypeptide, or polytyrosine (Poly-Tyr) that is a hydrophobic polypeptide, were connected to the carboxy terminus of Pseudomonas sp. esterase by the recombinant DNA technique. The hydrophobicity of the esterase was enhanced by the introduction of Poly-Pro or Poly-Tyr, and also by increasing chain length of the polypeptides. Poly-Tyr increased the hydrophobicity of esterase more than Poly-Pro. Poly-Tyr induced significant conformational change of fusion esterase, but Poly-Pro did not. Consequently, the introduction of Poly-Tyr led to loss of activity of the fusion enzyme to a negligible level. On the other hand, the Poly-Pro-fusion-esterase retained enzymatic activity and the hydrolytic activity (kcat/Km) of the fusion esterase carrying 40 proline residues (esterase-Pro40) relative to that of the wild-type esterase with the substrates p-nitrophenyl-propionate, -pentanoate, and -hexanoate was 1.76, 1.95, and 4.7, respectively. The results could be explained in terms of easier access of long-chain carboxylate to the fusion esterase compared to the wild-type esterase in aqueous solution.

Base Sequence↗
PubMed1995

The independent gene amplification of electrophoretically indistinguishable B esterases from the insecticide-resistant mosquito Culex quinquefasciatus.

Resistance to organophosphates in Culex mosquitoes is typically associated with increased activity of non-specific esterases. The commonest phenotype involves two elevated esterases, A2 and B2, while some strains have elevation of esterase B1 alone. Overexpression of the two B esterase electromorphs is due to gene amplification. Full-length cDNAs coding for amplified esterase B genes from a resistant Cuban strain (MRES, with amplified B1 esterase) and a Sri Lankan strain (PelRR, with amplified B2 esterase) of C. quinquefasciatus have been sequenced. In addition, a partial-length cDNA coding for a B esterase from an insecticide-susceptible Sri Lankan strain (PelSS) has been sequenced. All the nucleotide sequences and the inferred amino acid sequences show a high level of identify (> 95% at the nucleotide and amino acid level), confirming that they are an allelic series. The two B1 esterase nucleotide sequences (MRES and the previously published TEM-R [Mouches, Pauplin, Agarwal, Lemieux, Herzog, Abadon, Beyssat-Arnaouty, Hyrien, De Saint Vincent, Georghiou and Pasteur (1990) Proc. Natl. Acad. Sci. U.S.A. 87, 2574-2578]) showed the lowest identity, and restriction-fragment-length-polymorphism analysis of the two strains was different. On the basis of these data we suggest that the two electrophoretically identical B1 esterase isoenzymes from California and Cuba have been amplified independently. Alternatively, if amplification has occurred only once, the original amplification has not occurred recently.

Amino Acid Sequence↗
PubMed1987

Overproduction of detoxifying esterases in organophosphate-resistant Culex mosquitoes and their presence in other insects.

Antisera raised against the denatured polypeptide of two organophosphate-detoxifying esterases (B1 and A1) of Culex mosquitoes were used in an immunoblot method to quantify esterase production in resistant versus susceptible strains and to detect the presence of immunologically related proteins in other insects. It was demonstrated that esterase B1 of Culex quinquefasciatus and esterase A1 of Culex pipiens are overproduced in resistant strains by factors of at least 500-fold and 70-fold, respectively, as compared with the corresponding susceptible strains. These factors approximate the levels of resistance to the organophosphate chlorpyrifos determined by bioassay--i.e., about 800-fold and 100-fold, respectively. Antiesterase B1 antiserum was found to react with other type B esterases (B2 of C. quinquefasciatus and B3 of Culex tarsalis) but not with type A esterases (A1 of C. pipiens, A2 of C. quinquefasciatus, or A3 of C. tarsalis); similarly, antiesterase A1 antiserum was found to react with other type A esterases (A2 and A3) but not with type B esterases (B1, B2, and B3). Proteins immunologically related to esterase B1 were detected in Aedes aegypti L., Myzus persicae Sultzer, and Musca domestica L., although they were not overproduced in the organophosphate-resistant strains of these species. In none of these species were proteins immunologically related to esterase A1 found.

Animals↗
PubMed1984

Measurement of the rat urinary plasminogen activator (esterase A) by direct radioimmunoassay in urine and tissue.

Rat urinary esterase A, a plasminogen activator with kininogenase activity, was recently purified and characterized (J. Chao (1983) J. Biol. Chem. 258, 4434-4439). A sensitive radioimmunoassay for esterase A has been developed. This assay uses a rabbit antiserum in a final dilution of 1:160 000 and the purified enzyme was labelled with 125I using a lactoperoxidase method. It detects 80 pg of immunoreactive material per tube. This antiserum has some cross-reactivity with rat urinary kallikrein (approximately 5%) but a previously characterized tissue kallikrein antiserum has negligible cross-reactivity with the urinary esterase A in the assays. Therefore, kallikrein levels are measured simultaneously in all samples to obtain accurate levels of immunoreactive esterase A. Dilutions of urine or tissue homogenates showed complete parallelism with esterase A standard curves. No cross-reactivity with dog, human or monkey urine was seen. The recovery of esterase A from rat urine was 99.7 +/- 3.5%. Intra- and between-assay errors were 6.5 and 11.2%, respectively. Immunoreactive esterase A was measured and compared with kallikrein levels in rat urine, kidney, pancreas, submandibular gland, descending colon and ileum. The urinary esterase A excretion rate was reduced significantly in rats on a high sodium, compared with a low sodium diet, but not significantly increased above control by the latter. Nonetheless, a significant correlation between urinary kallikrein and esterase A excretion rate was present. This radioimmunoassay can now be used to measure esterase A levels in urine and tissue as questions have arisen about its regulation and functional significance.

Animals↗
PubMed2004

[Long-term toxicity test of arginine esterase from Agkistrodon halys ussuriensis venom].

To study the long-term toxicity of arginine esterase from Agkistrodon halys ussuriensis venom for the clinical application of arginine esterase in the future. Beagle dogs were used as experimental animals and were divided into control group, arginine esterase low dose group (0.06 u/kg), the middle dose group (0.18 u/kg) and high dose group (0.36 u/kg). Every group consisted of four dogs. The arginine esterase was given intravenously once a day for 180 days. Then three dogs in each group were sacrificed and the fourth one was fed without injecting arginine esterase for 15 days. The toxic reactions during treatment and recovery period were determined by evaluating and comparing the general criteria ( including locomotor activity, growth rate, appetite and death rate), clinical criteria (including blood test and urine test), pathological dissection and viscera coefficient of the treated animals and the control animals. There were no significant differences in general criteria. The clinical criteria of the treated animals were the same as those of the control animals except liver function. There were no significant differences in pathological dissection and viscera coefficient between the treated animals and the control animals except livers. The livers in high dose arginine esterase treated animals were swollen and vacuolated and there was significant difference in liver coefficient between them (P<0.05). The toxic symptom of liver disappeared after withdrawal of treatment. From these results, the non-toxic dose of arginine esterase for dogs was estimated to be 0.18 u/kg under the present study conditions and is about 15 times the clinical dosage for using the drug "Qingshuanmei" of which the main component is arginine esterase. The long-term toxicity test result indicates that the toxicity of pure arginine esterase is lower than that of "Qingshuanmei", suggesting that clinical use of the arginine esterase is safe.

Animals↗
PubMed1989

O-acetylation and de-O-acetylation of sialic acids. Sialic acid esterases of diverse evolutionary origins have serine active sites and essential arginine residues.

We and others have recently described 9-O-acetyl-sialic acid esterase (9-O-Ac-SA esterase) activities that appear to be specific for removal of O-acetyl esters from the 9-position of naturally occurring sialic acids. We have now examined a variety of species for such enzymes and found them in vertebrates and higher invertebrates, but not in plants or in lower invertebrates. This evolutionary distribution correlates well with that of the sialic acids themselves. All of the 9-O-Ac-SA esterase activities tested were inhibited by diisopropyl fluorophosphate (DFP) in a dose-dependent fashion. This indicates that each of these enzymes has a serine active site similar to the well known serine esterases and serine proteases. Methyl esterification of the carboxyl group of 9-O-acetyl-N-acetylneuraminic acid significantly reduced the activity of all of the 9-O-Ac-SA esterases against the O-acetyl group. This indicates that each of these enzymes may recognize the negatively charged carboxyl group of the sialic acid. Enzymes that recognize anionic substrates frequently have an essential arginine residue (Riordan, J. F., McElvany, K. D., and Borders, C. L., Jr. (1977) Science 195, 884-886). We therefore studied the effects of the arginine-specific modifying reagents 2,3-butanedione and phenylglyoxal on 9-O-Ac-SA esterase activities from influenza C virus, human erythrocytes, rat liver, starfish gonads, and sea bass brain. All of these enzymes were inhibited in a dose-dependent fashion by both reagents, under conditions previously known to avoid nonspecific modification. In contrast, the typical serine proteases trypsin and kallikrein and the serine esterase acetylcholinesterase were not significantly affected, even by the highest concentrations of these reagents used. These data indicate that five 9-O-Ac-SA esterase activities from evolutionarily distinct origins all have serine active sites and essential arginine residues. We postulate that the arginine residue is involved in substrate recognition via the negatively charged carboxyl group of the sialic acids. Thus, these 9-O-Ac-SA esterase activities may be members of a previously undescribed class of serine esterase.

Acetylation↗
PubMed2005

Polycarbonate-urethane hard segment type influences esterase substrate specificity for human-macrophage-mediated biodegradation.

Previous studies have shown that esterase activity can degrade a variety of polyurethanes (PUs), including polycarbonate-based PUs (PCNUs). When cultured on PCNUs, differing in their chemistries, monocyte-derived macrophages (MDM) synthesized and secreted different amounts of both cholesterol esterase (CE) and monocyte-specific esterase (MSE). MDM were seeded on PCNUs synthesized with hexane diisocyanate (HDI) or 4,4'-methylene-bis-phenyl diisocyanate (MDI), PCN and [14C]butanediol (BD) in the ratio 3:2:1 (referred to as HDI321 or MDI321). The effect of phenylmethylsulfonyl fluoride (PMSF, a serine esterase and proteinase inhibitor), sodium fluoride (NaF, a MSE inhibitor) and sodium taurocholate (NaT, a CE stimulator) was assessed on degradation (measured by radiolabel release (RR)) and esterase activity in MDM lysate. The results were compared to the effect that these reagents had on commercially available CE and carboxyl esterase (CXE), which has a specificity similar to MSE. NaF inhibited CXE- and MDM-mediated RR to the same extent as for both PCNUs. However, the MDM-mediated RR from MDI321 was 1.8-times higher than HDI321 in the presence of NaT (P = 0.005). This study suggests that the difference in diisocyanate chemistry may dictate the relative contribution of each esterase to a specific material's degradation. This may be related to both the substrate specificity of each esterase, as well as by the relative amount of each esterase that the specific biomaterial substrates induce the cells to synthesize and secrete.

Biocompatible Materials↗
PubMedDate not supplied

Induction of eosinophilic granules, nonspecific esterase activity and CD14 expression in the human eosinophilic leukemia cell line, EOL-1.

We examined the expression of eosinophilic granules, esterase activity and CD14 in a human eosinophilic cell line, EoL-1. Unstimulated EoL-1 cells were weakly positive for nonspecific esterase, but negative for surface CD14, and contained a few eosinophilic granule-positive cells. A combination of G-CSF and TNF-alpha increased the eosinophilic granule-containing cells, but failed to increase esterase activity or CD14 expression. IFN-gamma alone or in combination with TNF-alpha enhanced nonspecific esterase activity but failed to induce CD14 expression or increase eosinophilic granule-containing cells. dbcAMP increased eosinophilic granule-containing cells, nonspecific esterase activity and CD14 expression. Specific esterase activity was not detected in any circumstances. EoL-1 cells fractionated by density gradients or CD14 expression showed nonspecific esterase activity and CD14 expression in both the eosinophilic granule-positive and negative cell populations. Forskolin and butyrate had a synergistic effect on CD14 induction and protein kinase A was suggested to play a role in dbcAMP-induced CD14 expression. A protein kinase C activator, phorbol 12-myristate 13-acetate, did not increase eosinophilic granules, nonspecific esterase activity or CD14 expression in EoL-1 cells. The results show that EoL-1 cells can express nonspecific esterase and CD14, but the expression is not necessarily restricted to cells which have differentiated into the monocyte/macrophage lineage.

Antigens, CD↗
PubMed2006

Characterization of esterase activity in Geobacillus sp. HBB-4.

A thermophilic esterase producing bacterium (Bacillus sp. 4), recently isolated from Alangüllü thermal spring in Aydin (Turkey), was analyzed using 16S rRNA and classified as Geobacillus sp. HBB-4, most closely related to Bacillus sp. BGSC W9A59 (0.70% sequence divergence) which belongs to the newly described genus Geobacillus. The effects of several chemicals on the activity of thermostable esterase from Geobacillus sp. HBB-4 were examined. Among the various metal ions tested, esterase activity was enhanced by Mn(+2) and Ni(+2), but was inhibited by Hg(+2) and Cu(+2), whereas Ca(+2), Mg(+2) and Co(+2) had no effect. In addition, other metal ions studied have caused a slight inhibition on the esterase activity. EDTA partially inhibited the HBB-4 esterase. The activator metal ions, Mn(+2) and Ni(+2) have restored partial inhibition of EDTA. The activity of HBB-4 esterase was inhibited by ionic detergents while non-ionic detergents activated the enzyme. However, a zwitterionic detergent, CHAPS, has caused a slight inhibition in the enzyme activity. HBB-4 esterase activity was inhibited at the high concentrations of all the organic solvents tested in the present study. However, 50% final concentration of DMSO increased the enzyme activity about 7%. The HBB-4 esterase has shown more than about 50% of activity in the presence of ethanol and methanol solutions. These characteristics of the enzyme along with its significant thermostability make the Geobacillus sp. HBB-4 esterase a potent candidate for future industrial applications.

Bacillaceae↗
PubMed1977

Tissue-specific esterases in the Xiphophorine fish Platypoecilus maculatus, Xiphophorus helleri, and their hybrid.

Tissue-specific esterases of the xiphophorine fishes Platypoecilus maculatus (platyfish), Xiphophorus helleri (swordtail), and their F1 hybrid have been analyzed using disc electrophoresis. Seven esterase zones (resolved into a maximum of nine bands) exist in these fishes, and these have been classified by employing specific inhibitors. Five of the seven zones, EST-1, EST-2, EST-5, EST-6, and EST-7, appeared to be carboxylesterases; while the two remaining zones, EST-3 and EST-4, were classified as cholinesterases. In the liver of the platfish, all seven esterase zones were detected, while the liver of the swordtail exhibited only five esterase zones. EST-1 and EST-3 were lacking in the liver tissue of the swordtail. All seven esterase loci were expressed in the liver tissue of the F1 hybrid. The reciprocal crosses gave the same results. In the fin, skin, skeletal muscle, and eye tissues from all three genotypes, three major esterase zones, EST-2, EST-5, and EST-7, were detected. In addition, EST-1 was frequently detected in all these tissues of the platfish and the F1, but was lacking in the swordtail. Serum from three genotypes showed one prominent esterase zone, EST-5; however, trace activity of EST-2 and EST-7 zones could also be detected. It seems that in all tissues of the F1 hybrid there is expression of all the esterase genes from the platfish. The results of the present study are discussed in the comparison to those from other studies on teleost esterases.

Animals↗
PubMed1981

Differentiation of macrophages from Lewis lung carcinoma tumour cells in tissue sections by their alpha-naphthyl butyrate esterase activity.

The activities of alpha-naphthyl butyrate esterase, non-specific esterase, indoxyl esterase and acid phosphatase were studied histochemically in macrophages in cultures and in tissue sections of primary tumours and metastases of Lewis lung carcinoma (3LL). All macrophages in culture were stained by the alpha-naphthyl butyrate esterase procedure. In tissue sections, macrophages were intensely stained by the butyrate esterase procedure, while the tumour cells were not stained at all; macrophages were easily differentiated from 3LL cells. Non-specific esterase was evident in both tumour cells and macrophages. Indoxyl esterase and acid phosphatase were present in macrophages at the margin of the tumour only. The alpha-naphthyl butyrate esterase-positive macrophages differed in shape and location from acid phosphatase and indoxyl esterase-positive macrophages. This may indicate a difference in characteristics between macrophages found inside a tumour and those found at the tumour margins.

Acid Phosphatase↗
PubMed2002

Distinction between esterases and lipases: a kinetic study with vinyl esters and TAG.

The better to characterize enzymes hydrolyzing carboxyl ester bonds (carboxyl ester hydrolases), we have compared the kinetic behavior of various lipases and esterases against solutions and emulsions of vinyl esters and TAG. Short-chain vinyl esters are hydrolyzed at comparable rates by esterases and lipases and have higher limits of solubility in water than corresponding TAG. Therefore, they are suited to study the influence of the physical state of the substrate on carboxyl ester hydrolase activity within a large concentration range. Enzymes used in this study are TAG lipases from microorganisms, lipases from human and guinea pig pancreas, pig liver esterase, and acetylcholinesterase. This study also includes cutinase, a fungal enzyme that displays functional properties between esterases and lipases. Esterases display maximal activity against solutions of short-chain vinyl esters (vinyl acetate, vinyl propionate, and vinyl butyrate) and TAG (triacetin, tripropionin, and tributyrin). Half-maximal activity is reached at ester concentrations far below the solubility limit. The transition from solution to emulsion at substrate concentrations exceeding the solubility limit has no effect on esterase activity. Lipases are active on solutions of short-chain vinyl esters and TAG but, in contrast to esterases, they all display maximal activity against emulsified substrates and half-maximal activity is reached at substrate concentrations near the solubility limit of the esters. The kinetics of hydrolysis of soluble substrates by lipases are either hyperbolic or deviate from the Michaelis-Menten model and show no or weak interfacial activation. The presence of molecular aggregates in solutions of short-chain substrates, as evidenced by a spectral dye method, likely accounts for the activity of lipases against soluble esters. Unlike esterases, lipases hydrolyze emulsions of water-insoluble medium- and long-chain vinyl esters and TAG such as vinyl laurate, trioctanoin, and olive oil. In conclusion, comparisons of the kinetic behavior of carboxyl ester hydrolases against solutions and emulsions of vinyl esters and TAG allows the distinction between lipases and esterases. In this respect, it clearly appears that guinea pig pancreatic lipase and cutinase are unambiguously classified as lipases.

Acetylcholinesterase↗
PubMed1994

Increased cholesterol esterase level by cholesterol loading of rat pancreatoma cells.

This study used the rat pancreatoma AR42J cells as a model to determine the effects of cholesterol on cholesterol esterase biosynthesis. Incubation of AR42J cells with low-density lipoproteins (LDL) or with the cholesterol-induced beta-very-low-density lipoproteins did not result in changes in cellular cholesterol levels. These cholesterol-rich lipoproteins also had no effect on cholesterol esterase biosynthesis by the AR42J cells. Cellular cholesterol level was found to increase by approx. 2-fold after incubating the AR42J cells with cationized-LDL. The increase in cellular cholesterol level resulted in a higher level of cholesterol esterase secreted into the culture medium. The increased cellular cholesterol also resulted in higher amounts of cholesterol esterase detected in the AR42J cell lysate. The increase in cholesterol esterase level corresponded to a cholesterol-induced increase in steady-state level of cholesterol esterase mRNA. The results of this study, and our previous observation of post-transcriptional activation of cholesterol esterase induced by intestinal hormones (Huang, Y. and Hui, D.Y. (1991) J. Biol. Chem. 266, 6720-6725), suggested that cholesterol esterase biosynthesis may be regulated by transcriptional and translational mechanisms in response to hormonal and nutrient stimulation of the pancreatic acinar cells. Additionally, the regulation of cholesterol esterase biosynthesis by cholesterol loading of the pancreatic cells suggested a possible role of this enzyme in cholesterol metabolism.

Animals↗
PubMed1993

Effects of sodium fluoride and cobalt chloride on the enantioselectivity of microsomal and cytosolic esterases in rat intestinal mucosa.

The effects of sodium fluoride (NaF) and cobalt chloride (CoCl2) on the enantioselective hydrolysis of racemic oxazepam 3-acetate (rac-OXA) by microsomal and cytosolic esterases in rat intestinal mucosa were studied. Microsomal and cytosolic esterases hydrolyzed S-OXA and R-OXA in approximately 1:19 and 4:1 ratios, respectively. The hydrolysis of R-OXA by microsomal esterases was inhibited by NaF with an IC50 of 13.4 +/- 1.5 mM. Hydrolyses of both S-OXA and R-OXA by cytosolic esterases were inhibited by NaF with a similar IC50 value (approximately 3 mM). The hydrolysis of S-OXA by cytosolic esterases was inhibited by CoCl2 (IC50 = approximately 5 mM), whereas the hydrolysis of R-OXA by cytosolic esterases was stimulated by approximately 10% in the presence of 1 mM CoCl2. In comparison, the hydrolysis of R-OXA by microsomal esterases was stimulated by approximately 55% in the presence of 1 mM CoCl2. These results not only revealed the effects of NaF and CoCl2 on the catalytic activities of enantioselective cytosolic and microsomal esterases, but also indicated that microsomal and cytosolic esterases that selectively hydrolyzed R-OXA were distinctly different protein entities.

Animals↗