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PubMed1983

Esterase-type of activity possessed by human plasma apolipoprotein C-II and its synthetic fragments.

Human plasma apolipoproteins apo A-I, A-II, C-I, C-II and C-III (with the exception of apoE), porcine pancreatic colipase and procolipase hydrolyze 4-methylumbelliferyloleate. In all cases, liberation of 4-methylumbelliferone could be inhibited by phenylmethylsulfonyl-fluoride, thus suggesting the involvement of serine residues. To the best of our knowledge this is the first report on the esterase activities of these peptides. Synthetic fragments of the lipoprotein lipase activator, apoC-II, prepared according to the known sequence, also possessed this esterase-type of activity. Furthermore, the esterase-type of activities of the synthetic apoC-II fragments with different chain lengths bore a relatively good correlation to the reported abilities of these peptides to produce activation of lipoprotein lipase. We propose a model for the mechanism of activation of lipoprotein lipase by apolipoprotein C-II. ApoC-II would enhance the apparent catalytic rate constant of lipoprotein lipase by functioning as a specific acyl-enzyme hydrolase. A similar catalytic mechanism is suggested for other protein co-factors of hydrolytic enzymes.

Amino Acid Sequence↗

PubMed1992

Analysis of the catalytic mechanism of juvenile hormone esterase by site-directed mutagenesis.

1. Juvenile hormone esterase (JHE) is a serine hydrolase selective for hydrolysis of the conjugated methyl esters of insect juvenile hormones. 2. We have investigated the mechanism of catalytic action of this enzyme by site-directed mutagenesis of the cloned enzyme and expression of the mutants in a baculovirus system. 3. A series of individual mutations of JHE were made to residues possibly involved in catalysis of juvenile hormones, and which are highly conserved in both esterases and lipases. 4. Mutation of the serine residue at position 201 to glycine (S201G), or aspartate 173 to asparagine (D173N), or histidine 446 to lysine (H446K), removed all detectable activity and these mutagenized enzymes were determined to be at least 10(6)-fold less active than wild type JHE. 5. Mutation of arginine 47 to histidine (R47H) decreased but did not abolish activity, with Km essentially unchanged at 66 nM for R47H compared to 34 nM for wild type JHE. 6. The kcat for R47H was decreased from 103 min-1 for wild type JHE to 1.9 min-1. 7. In addition, glutamate residue 332 was altered to glutamine (E332Q) and expressed in an Escherichia coli system. 8. This mutation was also found to remove all detectable activity. 9. From the results presented in this study and by comparison of JHE to other serine esterases and lipases, we predict that JHE possesses a Ser201-His446-Glu332 catalytic triad. 10. In addition, aspartate 173 and arginine 47 are essential for the efficient functioning of JHE.

Amino Acid Sequence↗

PubMed1981

Aortic cholesterol esterase and other lysosomal enzyme activities in DOCA-salt, renal and spontaneous hypertension in the rat.

In spontaneously hypertensive rats, prolonged hypertension caused a decrease in aortic cholesterol esterase activity with N-acetyl-beta-D-glucosaminidase activity increased and acid phosphatase activity unchanged [3]. The present study was undertaken to compare these changes with those caused by other experimentally induced types of hypertension. Treatment with DOCA-salt for one month significantly elevated both aortic cholesterol esterase and acid phosphatase activities. In contrast, to spontaneous hypertension, venous changes were also observed. An intake of 1% NaCl ad libitum produced results similar to those with the DOCA-salt treatment, despite the fact that blood pressure did not increase. This suggested that humoral factors were the main cause of the elevated enzyme activities in DOCA-salt hypertension. In rats made hypertensive by unilateral renal arterial constriction with contralateral nephrectomy (one clip--one kidney hypertension) or without contralateral nephrectomy (one clip--two kidney hypertension), aortic cholesterol esterase activities were unchanged, while aortic N-acetyl-beta-D-glucosaminidase, and aortic and venous acid phosphatase activities were increased. These results show distinct differences in the response of lysosomal enzymes during the three hypertensive states.

Acetylglucosaminidase↗

PubMed1979

Esterase staining of human peripheral blood mononuclear cells.

Recently proposed esterase staining methods for the cytochemical identification of human peripheral blood monocytes and lymphocytes in our hands gave suboptimal results. Cellular purification and recommended fixation procedures appeared to decrease the esterase reactivity of leucocyte preparations. Drying for 12-18 h without further fixation of cytocentrifuge smears was found to produce minimal loss of the staining capacity for 1-naphthyl butyrate esterase in mononuclear cells. It is hoped that the slightly modified procedure meets the need for a simple technique to define mononuclear blood cells for clinical purposes.

Esterases↗

PubMed1984

Hydrolysis of pyrethroid insecticides by soluble mouse brain esterases.

trans-Permethrin, a pyrethroid insecticide, was hydrolyzed by one or more carboxylesterases located in the soluble fraction of mouse brain homogenates. The apparent affinity of this activity for trans-permethrin was greater than that reported for mouse hepatic carboxylesterase activity, but the apparent maximum velocity was considerably lower than that of the hepatic activity. Soluble brain esterases also hydrolyzed several other pyrethroid esters with a substrate specificity different from that of the hepatic esterases. In particular, alpha-cyano-3-phenoxybenzyl esters of noncyclopropane acids (e.g., fenvalerate and fluvalinate) were hydrolyzed by brain esterases at rates equal to or greater than that measured for trans-permethrin. These results suggest that hydrolysis in the brain may contribute to the detoxication of some pyrethroids in mammals.

Animals↗

PubMed1984

Induction of hepatic microsomal cytochrome P-450 and inhibition of brain, liver, and plasma esterases by an acute dose of S,S,S-tri-n-butyl phosphorotrithioate (DEF) in the adult hen.

The differential effects of oral and dermal administration of single doses of 100 to 1000 mg/kg S,S,S-tri-n-butyl phosphorotrithioate (DEF) on nonspecific esterases and liver metabolism enzymes were investigated one day following administration. O,O-Diethyl O-(4-nitrophenyl) phosphorothioate (parathion) and tri-o-cresyl phosphate (TOCP) were used as negative and positive controls for organophosphorus-induced delayed neurotoxicity (OPIDN). Brain acetylcholinesterase was significantly inhibited with topical doses of 500 and 1,000 mg/kg of DEF and with orally and dermally applied parathion. Plasma cholinesterase and liver microsomal carboxylesterase activities were significantly reduced from control in all treatment groups. Neurotoxic esterase (NTE) was significantly decreased from control with topical dosing of 200, 500, and 1000 mg/kg DEF and with TOCP treatments. Oral doses of DEF increased cytochrome P-450 content by 70 to 200% while dermal application caused a 200 to 325% increase over control. p-Chloro-N-methylaniline demethylase was also increased by DEF treatments but to a lesser extent than that of aniline hydroxylase or cytochrome P-450 content. TOCP and parathion had no significant effect on liver microsomal oxidative enzymes. Liver microsomal proteins from hens treated with phenobarbital (PB), 3-methylcholanthrene (3MC), or DEF were analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. A striking increase in a 49K protein band in microsomes from PB and DEF (616 and 338%, respectively) treated hens was seen, while the 55K protein band showed an 861% increase in microsomes from 3MC-treated hens. In conclusion, dermally applied DEF was more effective in inhibiting esterases and inducing cytochrome P-450 than orally administered DEF; toxicity was directly related to the dose and route of administration.

Administration, Oral↗

PubMed1980

A rapid spectrophotometric method for the determination of esterase activity.

We have developed a spectrophotometric assay method which continuously records esterase activity at 510 nm by monitoring absorbance changes due to the formation of a diazo dye complex. In our method, alpha-naphthyl ester substrates are hydrolyzed by enzymatic action to alpha-naphthol which couples to Fast Blue RR salt (a diazonium salt) forming a diazo dye complex. Our method is unique in directly monitoring the formation of the diazo dye complex without extracting the color of the complex as in other methods that use naphthyl esters and diazo coupling of reaction products. The method appears to be limited to alpha-naphthyl ester substrates, however, since beta-naphthyl esters did not give a linear change in absorbance in the enzymatic reactions tested. With this assay method, one can use a single substrate both to determine esterase units quantitatively in solution and to detect esterase staining activity on gel electrophoresis.

Animals↗

PubMed1983

Porcine cholesterol esterase, a multiform enzyme.

Cholesterol esterase (sterol-ester acylhydrolase, EC 3.1.1.13) has been purified from porcine pancreas by two methods, one of which was previously reported by Momsen, W.E. and Brockman, H.L. (Biochim. Biophys. Acta. 486 (1977) 102-113). Multiple forms of the enzyme were demonstrated throughout the course of both purification procedures. These forms hydrolyzed both p-nitrophenyl acetate as well as cholesteryl oleate. Isoelectric focusing was used to select one form of cholesterol esterase having a pI of 4.3 for further study. Using high-pressure liquid chromatography on a TSK Spherogel column this apparently homogeneous preparation of cholesterol esterase was separated into two components having molecular weights equal to 90 000 (peak I) and 45 000 (peak II). The number of each amino acid residue in peak I was double that of the corresponding residue in peak II, suggesting a dimer-monomer relationship. The N-terminal analyses showed that the first five amino acid residues were the same in peak I and peak II. The enzyme is a glycoprotein containing glucosamine, glucose, galactose, mannose and rhamnose; it is inhibited by diisopropyl fluorophosphate.

Amino Acid Sequence↗

PubMed1989

Studies of the action of symmetrical and mixed disulphide thiol-modifying reagents on the esterase activity of cytoplasmic aldehyde dehydrogenase.

The effect of various thiol-modifying reagents on the esterase activity of sheep liver cytoplasmic aldehyde dehydrogenase is reported here. Both symmetrical reagents (disulfiram, 2,2'- and 4,4'-dithiodipyridines) and unsymmetrical reagents (methyl diethylthiocarbamyl disulphide, methyl 2- and 4-pyridyl disulphides) were investigated. The results suggest that all the modifiers react to varying extents with a pair of enzymic thiol groups ('A' and 'B'), and that the more specifically group 'A' is modified, the more the enzyme is inactivated. This supports the idea that group 'A' may be the essential nucleophile in the reaction catalysed by aldehyde dehydrogenase. Modification of group 'B' may or may not reduce the esterase activity depending on the nature of the label introduced. The results of the present experiments and of previous similar experiments concerning the dehydrogenase activity of the enzyme are consistent with the proposal that a common active site is responsible for both esterase and dehydrogenase activities.

Aldehyde Dehydrogenase↗

PubMed1995

Catalytic properties of rabbit serum esterases hydrolyzing esterified monosaccharides.

Rabbit serum and one enzyme fraction isolated from rabbit serum by column chromatography (Fraction II) were used as catalysts in regioselective hydrolysis of radiolabelled pivaloylated monosaccharides (Piv = Me3CCO). The hydrolysis of 14C-labelled methyl 2-O-pivaloyl-(2-MP)-, 6-O-pivaloyl (6-MP)-, 2,6-di-O-pivaloyl-(2,6-DP) alpha-D- glucopyranosides and methyl 2-acetamido-2-deoxy-3,6- di-O-pivaloyl-(3,6-DPNAc) alpha-D-glucopyranosides, was studied, as well as that of the non-sugar substrates butyrylthiocholine, thiophenylbutyrate, phenylacetate and paraoxon. The specific activities of 2,6-DP, 3,6-DPNAc, butyrylthiocholine and thiophenylbutyrate were higher in Fraction II than in native sera, while those of phenylacetate and paraoxon were lower. Inhibition studies were done using the substrates mentioned and five different inhibitors, namely bis(p-nitrophenyl phosphate) (BNPP), eserine, paraoxon, HgCl2 and EDTA. The hydrolysis of 2,6-DP and 3,6-DPNAc was not inhibited by HgCl2 and only slightly by EDTA. Paraoxon, eserine and BNPP were progressive inhibitors of the hydrolysis of the two sugar substrates, and the pattern of inhibition resembled closely the inhibition of butyrylthiocholine and thiophenylbutyrate hydrolysis. This result applied to both, native serum and Fraction II. It was concluded that esterases in rabbit serum which hydrolyze pivaloylated sugar substrates belong to the category of serine esterases. Kinetic parameters (KM and Vmax), effects of temperature and pH on activity of esterases from Fraction II were also determined for the hydrolysis of sugar substrates.

Animals↗

PubMed1978

Common and species-specific esterases of Equidae--IV. Horse of przewalski, onager and Zebra hartmannae.

1. Among several species of Equidae only E. przewalskii possesses a serum esterase identical with that of E. caballus. 2. The esterases of Hemionidae differ slightly from that of domestic horse by electrophoretic migration and by antigenic structure. 3. Zebras (grevyi, burchelli) appear devoid of this component but Z. hartmannae possesses an esterase of high enzymatic activity, differing notably from that of horse by electrophoretic and antigenic properties.

Animals↗

PubMed1987

Enzymatic deacylations of esterified saccharides. II. De-esterifications of radiolabelled O-acylglucopyranosides by mice serum and liver esterases.

1. 14C-Labelled methyl 2,6-di-O-pivaloyl-alpha-D-glucopyranoside (1) was used as a novel substrate for esterases from mouse serum and liver. 2. Stepwise de-esterification of the diester substrate 1 was achieved, and data on time-course experiments are reported. 3. Kinetic studies were undertaken to compare deacylation rates for the enzymatic de-esterification of the diester substrate 1 using both, mice sera and liver microsomal fractions. 4. Serum and liver esterase activities were studied in mice treated with an immunostimulating agent, peptidoglycan monomer (PGM), and a comparison made with esterases from untreated mice.

Acylation↗

PubMed1992

Esterase electrophoresis compared with biotyping for epidemiological typing of Acinetobacter baumannii strains.

Forty-nine Acinetobacter baumannii strains belonging to three biotypes and isolated from four hospitals were differentiated by electrophoretic typing of their esterases. Six main kinds of esterases were distinguished by their spectra of hydrolytic activity toward seven synthetic substrates. The electrophoretic variations of these enzymes were used to define ten zymotypes among the three biotypes. Esterase electrophoresis appeared to be more sensitive than biotyping, and could represent an additional marker for epidemiological analysis.

Acinetobacter↗

PubMed1992

Regulation and secretion of an extracellular esterase from Streptomyces scabies.

Production of a heat-stable, extracellular esterase by Streptomyces scabies is regulated by zinc ions. The esterase-encoding gene (est) from S. scabies was cloned and expressed in Streptomyces lividans. In S. lividans, expression of the est gene is also regulated by Zn2+, and the esterase is efficiently secreted in this organism. The sequence of the est gene suggests that a 39-amino acid signal peptide is removed during secretion of this protein. Deletion analysis has indicated that the hydrophobic domain of the signal peptide is required for secretion. Gel retardation assays and DNaseI footprinting using an S-30 protein extract from S. scabies have previously identified a specific 23-bp protein-binding site upstream from the est coding sequence. Deletion of this protein-binding sequence significantly decreased expression of the est gene.

Amino Acid Sequence↗

PubMedDate not supplied

Effect of repeated oral administration of quinalphos on blood esterases in Bubalus bubalis.

The effect of quinalphos on blood esterases was investigated in male buffalo calves after daily oral doses of 0.7, 1.4 and 2.1 mg/kg body weight for 28 consecutive days. Quinalphos markedly inactivated serum carboxylesterase (69-90%) and plasma cholinesterase activity (75-88%). Esterase activities in animals receiving 0.7 mg/kg/day of quinalphos approached normal levels 14 days after the termination of its ingestion. The results suggest that quinalphos is an effective inhibitor of blood esterases in vivo and its repeated exposure to buffaloes may impair detoxification of organophosphorus insecticides that are mainly biodegraded by carboxylesterase enzyme.

Administration, Oral↗

PubMed1985

Improved urine screening using a combination of leukocyte esterase and the Lumac system.

Three rapid urine screening tests, leukocyte esterase, nitrite, and the Lumac System for detection of bacterial ATP, were evaluated alone and in combination to determine their utility in screening urine specimens from male patients for bacteruria. The combination of leukocyte esterase and Lumac testing resulted in significant improvement in the sensitivity of urine screening over each test individually and the combination of leukocyte esterase and nitrite. The leukocyte esterase/Lumac combination detected 98% of those specimens with greater than or equal to 10(5) CFU/ml and had a negative predictive value of 99%. The results obtained from this type of testing can be used with confidence to minimize the number of urine specimens cultured and to provide rapid reporting of negative results.

Adenosine Triphosphate↗

PubMed1991

Elevated esterase activity in resistant tufted apple bud moth, Platynota idaeusalis (Walker) (Lepidoptera: Tortricidae).

1. Esterase activity in the tufted apple bud moth was measured spectrophotometrically by the hydrolysis of alpha-naphthyl acetate. 2. Resistant populations from both laboratory and field exhibited significantly greater esterase activity than did the respective susceptible populations. 3. The resistant laboratory population had significantly higher esterase activity than the resistant field population, suggesting that this field population contained a mixture of resistant and susceptible individuals.

Animals↗

PubMed1991

Partial characterization of soluble esterase from Heterodera glycines and inhibition by aldicarb and phenamiphos.

1. Homogenates of tissues from females of the nematode Heterodera glycines were clarified by centrifugation and used to initiate characterization of soluble esterases using p-nitrophenyl acetate as the substrate. 2. Optimum temperature and pH were 40 degrees C and 7.2 respectively. 3. Acetazolamide (a carbonic anhydrase inhibitor) at 10(-3) M did not inhibit enzyme activity, indicating that carbonic anhydrase was not present. 4. Phenamiphos (an organophosphate) at 10(-6) M reduced activity by 38%, whereas eserine hemisulfate (a cholinesterase inhibitor) and aldicarb (a carbamate) were not inhibitory at that concentration, indicating that there was no cholinesterase activity. 5. Eserine hemisulfate, aldicarb, and phenamiphos inhibited enzyme activity by 50% (I50) at 5 x 10(-3) M, 7.5 x 10(-4) M, and 6 x 10(-6) M, respectively. 6. Approximately 25% of the activity detected appeared due to A- and/or C-esterases. 7. The data demonstrated that aldicarb and phenamiphos were active against esterases other than acetylcholinesterase.

Acetazolamide↗