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PubMed1975

Human liver aldehyde dehydrogenase. Esterase activity.

Human liver aldehyde dehydrogenase has been found to be capable of hydrolyzing p-nitrophenyl esters. Esterase and dehydrogenase activities exhibited identical ion exchange and affinity properties, indicating that the same protein catalyzes both reactions. Competitive inhibition of esterase activity by glyceraldehyde and chloral hydrate furnished evidence that p-nitrophenyl acetate was hydrolyzed at the aldehyde binding site for dehydrogenase activity. Pyridine nucleotides modified esterase activity; NAD+ accelerated the rate of p-nitrophenyl acetate hydrolysis more that 5-fold, whereas NADH increased activity by a factor of 2. Activation constants of 117 muM for NAD+ and 3.5 muM for NADH were obtained from double reciprocal plots of initial rates as a function of modifier concentration at pH 7. The kinetics of activation of ester hydrolysis were consistent with random addition of pyridine nucleotide modifier and ester substrate to this enzyme.

Aldehyde Oxidoreductases↗

PubMed1991

[Determination of the esterase activity of serine proteinases using synthetic substrates].

The authors suggest a highly sensitive rapid and simple method for measuring esterase activities of bovine pancreatic chymotrypsin, human neutrophilic cathepsin D, and elastase, and of human blood serum chymotrypsin-like esterase and elastase-like esterase activities, with fluorogenic synthetic ethers, amino acid derivatives, employed as substrates: N-benzoxycarbonylphenylalanine 4-methylumbelliferyl ester (Z-Phe-OMC) and tret-butyloxycarbonyl-1-alanine 4-methylumbelliferyl ester (BOC-Ala-OMC).

Animals↗

PubMed1991

[A fluorometric method of determining cholesterol esterase activity].

A simple and highly specific method for estimating the cholesterol esterase activity is suggested. Cholesterol esterase (EC 3.1.1.13) is incubated with the emulsified substrate, cholesteryl-o-coumarate, at pH 6.6 to yield o-coumaric (trans-2-hydroxycinnamic) acid detected fluorimetrically (lambda exc 363 nm, lambda em 494 nm) at pH 10.4. The fluorescence associated with the unhydrolyzed substrate is negligible. Cholesteryl-o-coumarate is not hydrolyzed by pancreatic lipase, trypsin, or chymotrypsin under the above conditions. About 1 microgram of pancreatic cholesterol esterase can be determined upon 15 min incubation. The substrate was synthesized by condensation of o-acetoxy-trans-cinnamic acid with cholesterol using the di-tert-butyl pyrocarbonate--pyridine--4-dimethylaminopyridine system.

Animals↗

PubMed1991

A lux-specific myristoyl transferase in luminescent bacteria related to eukaryotic serine esterases.

The diversion of fatty acids from fatty acid biosynthesis into the luminescent system is catalyzed by a lux-specific acyltransferase that catalyzes the cleavage of fatty acyl-acyl carrier protein (ACP). Analysis of the substrate specificities for fatty acyl-ACPs of the transferases from divergent luminescent bacteria, Photobacterium phosphoreum and Vibrio harveyi, has demonstrated that myristoyl-ACP is cleaved at the highest rate. Inhibition by phenylmethanesulfonyl fluoride as well as resistance of the acylated enzyme intermediate to cleavage by hydroxylamine showed that the transferase is a serine esterase. Moreover, activity was dependent on a basic residue with a pKa of 6.3 implicating a histidine residue as part of a charge relay system found in serine esterases. The nucleotide sequence of the P. phosphoreum luxD gene coding for the transferase was determined resulting in the identification of the active site motif for serine esterases, G-X-S-X-G. Replacement of the serine residue at the center of this motif by threonine, alanine, or glycine blocked the transferase acyl-ACP cleavage activity, its ability to be acylated, and complementation of a transferase defective mutant on transconjugation with the luxD gene. The sequence and location of the serine as well as a histidine residue in the lux-specific transferases were found to be similar to those involved in the charge relay system in vertebrate thioesterases. Combined with the similar kinetic properties, these results support a common metabolic role for both enzymes in the diversion of fatty acids from the fatty acid biosynthetic pathway.

Acyl Carrier Protein↗

PubMed1990

Effect of esterase inhibition on the disposition of zomepirac glucuronide and its covalent binding to plasma proteins in the guinea pig.

The disposition of zomepirac (Z) and its acyl glucuronide metabolite were studied in rabbits and guinea pigs to determine if hydrolysis of zomepirac glucuronide (ZG) by tissue esterases occurs in vivo and what effect inhibition of esterases would have on exposure to ZG and subsequent covalent binding to plasma proteins. ZG was hydrolyzed rapidly in vivo by both guinea pigs and rabbits, liberating Z. The effect of inhibition of tissue esterases was determined by administration of phenylmethylsulfonyl fluoride (PMSF) concurrently with i.v. doses of Z or ZG to anesthetized, bile duct ligated guinea pigs. Administration of PMSF decreased the apparent plasma clearance of ZG by 86% and elevated the apparent plasma clearance of Z by 300%. Exposure of the guinea pigs to ZG as measured by the area under the plasma concentration vs. time curve (AUC) was increased substantially by PMSF treatment. Covalent binding of Z to plasma proteins in the guinea pig correlated well with AUC of ZG, but not with AUC of Z. The correlation of Z covalent binding with AUC of ZG in the guinea pig is similar to that found in humans suggesting that the degree to which acyl glucuronides form covalent adducts with proteins in humans may be predictable from studies in animals.

Anesthesia↗

PubMed1985

[Inhibition of liver lysosomal cholesterol esterase activity in rats by dextran blue in vivo and in vitro].

Dextran blue decreases the activity of lysosomal acid cholesteryl esterase of rat liver at a concentration from 0.25 M to 10 M without altering acid phosphatase, acid beta-galactosidase and beta-glucosidase activities. The dextran blue filled lysosomes with a high degree of purity prepared by centrifugation over the linear sucrose density gradient contained insignificant impurities (up to 19%) of protein from other organelles. The specific activity of acid phosphatase, beta-galactosidase and beta-glucosidase was increased 35-40-fold in this fraction, whereas the activity of acid cholesteryl esterase rose but 14.7-fold. Chromatography on a Sepharose 2B column of the digitonin-digested native and dextran-containing lysosomes attests to the formation of large dextran aggregates with lysosomal matrix proteins. Since aggregation of dextran blue with acid phosphatase, beta-galactosidase and beta-glucosidase does not affect their activities, it is concluded that to bring about hydrolysis of lipoprotein cholesterol esters, it is necessary that cholesteryl esterase be associated with hydrophobic macromolecules. Moreover, dextran blue can be used for simulation cholesterol esters deposition in lysosomes.

Animals↗

PubMed1989

Implications of probability analysis for interpreting results of leukocyte esterase and nitrite test strips.

We examined 288 urine samples, using test strips, sediment microscopy, and culture. The ability of the leukocyte esterase and nitrite test strips to detect or exclude urinary tract infection, as defined by a positive culture, was evaluated by probability analysis. We found that the diagnostic efficiency of the esterase-nitrite combination was similar to that of sediment microscopy. Moreover, once the strip test results had been obtained, little additional information was given by microscopy. The importance of estimating the prevalence, or pre-test probability, of infection before the test result is evaluated is emphasized. We conclude that, for detecting or excluding urinary-tract infection, microscopy can be replaced by the esterase and nitrite test strips. If the probability of infection predicted by the test strips is not high (or low) enough compared with medical decision limits, the samples should be cultured.

Esterases↗

PubMed1989

[Cytotoxic molecules, perforin and serine esterase in cytotoxic T lymphocyte].

Cytotoxic T lymphocyte (CTL) contains two cytotoxic molecules, perforin and serine esterase, in its cytoplasmic granules. These molecules play a key role in CTL-mediated cell lysis, but the precise mechanism has not been fully understood. The author has discovered some of the biochemical characteristics of these cytotoxic molecules. The molecular weight of purified perforin was 66 kd under reducing conditions. Its activity was absolutely dependent on the Ca2+ concentration. The highest activity was seen at 0.2 mM Ca2+ concentration. The Zn2+ ion inhibited the perforin activity in the presence of Ca2+ ion. Heparin increased the pore-forming activity of perforin with highest stimulation at 400 ng/ml. The perforin inhibitor protein, having a molecular weight of 500 kd, was isolated from human serum. This inhibitor suppressed the membrane-binding activity of perforin. The CTL-specific serine esterase detected with the substrate BLT had a molecular weight of 66 kd determined by HPLC gel filtration. The author found that the localization of BLT serine esterase was distinct from that of perforin in CTL. A study into the significance of the difference in the localization of the two molecules is now in progress.

Animals↗

PubMed1986

Genetics of esterases and 6-phosphogluconate dehydrogenase in the Anopheles maculatus complex.

Electromorphic variation for some esterases and 6-phosphogluconate dehydrogenase enzymes in the Anopheles maculatus complex is controlled by four loci which are unlinked to sex. Esterase loci are linked to each other: Est-1-36%-Est-4-16.5%-Est-3; but unlinked to Pgd-2. Linkage data were obtained by selfing the F1 generation from selected parents and analysing genotypes in the F2; the classical dihybrid-cross. The analysis consists of testing observed data for goodness of fit to a) ratios expected from Mendelian ratios without linkage and b) if they do not fit then computing a likely degree of linkage and computing expected ratios with such linkage for further tests. Confidence limits are given for the most likely levels of linkage. This method can provide useful information for population-genetic studies on anopheline mosquitoes, whose laboratory rearing is generally difficult. Through indirect evidence, the enzyme loci are correlated to polytene chromosomes. The esterases probably lie on chromosome three (polytene arms 3 and 4) and Pgd-2 on the second chromosome (arms 2 and 5).

Animals↗

PubMed1977

[Bodily heat resistance and polymorphism of liver esterases of grass frogs].

The determination of organismal heat resistance and qualitative composition of polymorphous liver esterases during heat acclimation (25 degrees) has been made on frogs Rana temporaria. During hybernation the most heat resistant frogs possess the homozygous allele of A2 esterase. Heat acclimation and the summer rise in temperature in nature lead to an increase in heat resistance of frogs and to the disappearance of selective advantage of animals possessing the isoenzyme of the A2A2 esterase. The functional homeostasis of populations can maintain biochemical polymorphism regardless of the selective advantage of individuals possessing one of the homozygous alleles of the isoenzyme.

Animals↗

PubMedDate not supplied

[Esterase activity of hydrocarbon-oxidizing bacteria].

The activity of esterase was studied in bacteria oxidizing hydrocarbons and belonging to the genera Rhodococcus, Arthrobacter and Pseudomonas. Indophenyl acetate was used as a substrate of the reaction catalysed by the enzyme. Exocellular esterases were not found. Endocellular esterases differed in their activity and thermostability both among the genera and among species of one and the same genus.

Arthrobacter↗

PubMed1987

Effects of esterase inhibitors and buthionine sulfoximine on the prevention of acetaminophen hepatotoxicity by N-acetylcysteine.

Mice poisoned with acetaminophen were treated with esterase inhibitors, buthionine sulfoximine, and N-acetyl-L-lysine in experiments designed to explore the mechanism of N-acetylcysteine protection in vivo. Three esterase inhibitors, phenylmethylsulfonyl fluoride, bis-(p-nitrophenyl)-phosphate, and diisopropylfluorophosphate, had no effect on the antidote effectiveness of N-acetylcysteine, although each provided partial protection against acetaminophen poisoning. Buthionine sulfoximine, a specific inhibitor of gamma-glutamyl cysteine synthetase, antagonized the antidote effect of N-acetylcysteine. Acetaminophen-induced hepatotoxicity, as measured by plasma alanine aminotransferase activity, and mortality failed to decline, consistent with stimulation of glutathione synthesis as the primary mechanism of antidote protection. N-Acetyl-L-lysine was given at doses up to ten-fold higher than N-acetylcysteine yet had no effect on acetaminophen hepatotoxicity or its prevention by N-acetylcysteine. These results advance the view that N-acetylcysteine acts primarily as a glutathione precursor. They further suggest the esterase inhibitors limit poisoning by acetaminophen and may be useful agents in antagonizing the toxicity of other metabolically activated drugs.

Acetaminophen↗

PubMed1988

[Cholesterol esterase activity of blood monocytes and the main risk factors of ischemic heart disease in men aged 20-59].

Changes in the activity of blood monocytic cholesterol esterase in men with major CHD risk factors (dyslipoproteinemia, arterial hypertension, excessive body mass) were described. Standard methods of epidemiological survey and a radionuclide method to determine cholesterol esterase activity applied to a representative sampling (195 persons) have shown that enzymatic activity was growing with age. In examinees with hyperlipoproteinemia of type IIa and IIb the activity of cholesterol esterase was decreased, and in persons with excessive body mass it was increased. In combination of 2-3 CHD risk factors significant differences in enzymatic activity were undetectable.

Adult↗

PubMedDate not supplied

[Isolation and various properties of immobilized cholesterol esterase].

Immobilization of cholesterol esterase enabled to study the enzymatic modification of blood serum lipoproteins during their interaction with cells. Due to high affinity of octyl-Sepharose to cholesterol esterase large volumes of diluted enzyme preparations were immobilized without preliminary concentration. After immobilization the enzyme pH optimum was unaltered, whereas the activating effect of low NaCl concentrations and inhibitory effect of the salt high concentrations were not observed. The immobilized on octyl-Sepharose cholesterol esterase exhibited the greater stability as compared with the enzyme diluted preparation and was used repeatedly without distinct decrease in activity.

Carboxylic Ester Hydrolases↗

PubMed1987

[Stimulating effect of cocaine in rats with different levels of blood esterase activity].

It was shown in experiments on male random-bred rats that motor stimulating effect of cocaine (10 mg/kg, intraperitoneally) was dependent on the spectrum of blood serum esterase activity. The determination of esterase spectrum was performed by disc-electrophoresis in 7.5% PAAG (50-75 gamma of protein per gel), with enzyme activity estimated using alpha-naphthylacetate. Proserine (10(-5) M) and butyrylthiocholine controls were used. Motor stimulating effect of cocaine in animals with 3 esterase fractions was 3 times higher than in animals with 4 enzyme fractions.

Animals↗

PubMed1987

Isolation and characterization of a 60-kilodalton glycoprotein esterase from liver microsomal membranes.

A glycoprotein having a subunit weight of approximately 60,000 was isolated from rabbit liver microsomes. It is a predominant component of the hepatic microsomal membrane and reacts rapidly with diisopropylphosphorofluoridate (DFP), resulting in the loss of enzymatic activity toward artificial substrates such as acyl esters of o-nitrophenols. Automated Edman degradation of this protein together with sequence analysis of peptides provided the NH2-terminal sequence of some 70 residues as follows: His-Pro-Ser- Ala-Pro-Pro-Val-Val-Asp-Thr-Val-Lys-Gly-Lys-Val- Leu-Gly-Lys-Phe-Val-Ser-Leu-Glu-Gly-Phe-Ala-Gln- Pro-Val-Ala-Val-Phe-Leu-Gly-Val-Pro-Phe-Ala-Lys- Pro-Pro-Leu-Gly-Ser-Leu-Arg-Phe-Ala-Pro-Pro-Gln- Pro-Ala-Glu-Ser-Trp-Ser-His-Val-Lys-Asn (CHO)- Thr-Thr-Ser-Tyr-Pro-Pro-Met-Cys-Ser-Ser. A carbohydrate attachment was identified at asparaginyl residue 61. The COOH-terminal peptide of the protein was isolated from two independent enzymatic digests, and its sequence was established as Arg-Glu-Thr-Glu-His-Ile-Glu-Leu. In order to isolate the DFP binding peptide, liver microsomes were labeled with [3H]DFP and the 60-kDa protein containing covalently bound DFP isolated in pure form. Following reduction and carboxymethylation, the DFP-labeled protein was fragmented with trypsin and the digest subjected to gel filtration. Digestion of the labeled peptide preparations with chymotrypsin followed by chromatography of the digest yielded two diisopropylphosphoryl (DIP) peptides. Automated Edman degradation of these peptides provided the following amino acid sequences: Gly-Glu-DIPSer- Ala-Gly-Gly-Gln-Ser-Val-Ser-Ile-Leu-Leu-Leu-Ser- Pro and Thr-Val-Ile-Gly-Asp-DIPHis-Gly-Asp-Glu-Ile-Phe. The active site serine peptide of the 60-kDa protein shows some 70% similarity to the active center region of choline esterases. While the postulated active histidyl residue in choline esterases has not been identified, it is proposed that the DFP binding histidine of the 60-kDa protein corresponds to His-438/440 of choline esterases.

Amino Acid Sequence↗

PubMed1987

Monocyte esterase? A factor involved in the pathogenesis of lymphoproliferative neoplasia.

Monocyte esterase activity was studied in 1,000 doctor-attending patients with normal hematological indices and in 56 patients with non-Hodgkin's lymphoma (NHL) or B chronic lymphocytic leukemia (CLL). The incidence of esterase deficiency was significantly greater in the NHL-CLL patients (7.1%) than in the population group (1.7%; p less than 0.05). In the NHL-CLL group, study of the families showed the esterase deficiency to be a familial characteristic. We postulate that the presence of the anomaly may be either a factor predisposing to the development of the NHL or CLL or a factor indicating a predisposition to these disorders.

Esterases↗

PubMed1986

Applicability of leukocyte esterase test strip in detection of canine pyuria.

A commercially available leukocyte esterase assay was evaluated for application in analyzing canine urine for the detection of pyuria. In 229 urine samples, the leukocyte esterase activity was compared with leukocyte concentrations, as assessed by microscopic sediment analysis and chamber cell counts. The leukocyte esterase assay was specific (93.2%) for canine pyuria, but was poorly sensitive (46.0%) and did not appear to be applicable to analysis of canine urine samples.

Animals↗