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PubMed1986

Kinetics of substrate hydrolysis and inhibition by mipafox of paraoxon-preinhibited hen brain esterase activity.

For the purpose of assessing the neurotoxic potential of organophosphorus compounds, it has been determined that paraoxon-preinhibited hen brain has both neurotoxicant (mipafox)-sensitive (neurotoxic esterase; NTE) and -insensitive esterase components. Several experiments designed to investigate the kinetic parameters governing the reaction of these esterases with two substrates and one organophosphorus inhibitor are presented. First, kinetic parameters for the hydrolysis of phenyl valerate and phenyl phenylacetate were measured. At 37 degrees C, the Km values of NTE for phenyl valerate and phenyl phenylacetate were found to be about 1.4 X 10(-3) and 1.6 X 10(-4) M respectively. At 25 degrees C, the Km of NTE for phenyl valerate was determined to be about 2.4 X 10(-3) M. Secondly, the kinetic constants of NTE for mipafox were measured at both 25 degrees C and 37 degrees C. With either phenyl valerate or phenyl phenylacetate as substrate, the Km at 37 degrees C was determined to be about 1.8 X 10(-4) M, and the phosphorylation constant (k2) was about 1.1 min-1. For phenyl valerate only, the Km at 25 degrees C was found to be about 6 X 10(-4) M, and the k2 was about 0.7 min-1. The data obtained at 25 degrees C were analysed by using a two-component model without formation of Michaelis complex, a two-component model with formation of Michaelis complex on the second component (NTE), or a three-component model without formation of Michaelis complex. The fact that the Michaelis model fit the data significantly better than either of the other two models indicates that the higher apparent Ki values that occur with low concentrations of mipafox are due to formation of Michaelis complex at high concentrations, rather than because of the presence of two NTE isoenzymes, as has been suggested by other investigators.

Animals↗
PubMed1994

Purification and some characteristics of the acetylxylan esterase from Schizophyllum commune.

Acetylxylan esterase from Schizophyllum commune was purified using ion-exchange and hydrophobic chromatography. The enzyme has a molecular mass of 31 kDa, as determined by SDS/PAGE, or 18 kDa, according to gel filtration. Glycosylation of the enzyme was not detected. Acetylxylan esterase is relatively stable under laboratory conditions; it retains full activity at pH 6.2-8.5 upon incubation at 25 degrees C for 7 h, but loses nearly the whole activity upon incubation at 60 degrees C for 30 min. The pH optimum of the enzyme activity is 7.7 and its temperature optimum lies between 30 and 45 degrees C. Ca2+ and Co2+ inhibit markedly the activity of acetylxylan esterase at a concentration of 10 mM, as do Mn2+, Zn2+, Fe2+ and Cu2+ at a concentration of 1 mM.

Acetylesterase↗
PubMed2001

The catalytic domain of human neuropathy target esterase mediates an organophosphate-sensitive ionic conductance across liposome membranes.

In humans and other vertebrates, reaction of organophosphates with a neuronal membrane protein, neuropathy target esterase (NTE), initiates events which culminate in axonal degeneration. The initiation process appears to involve modification of a property of the protein distinct from its esterase activity, subsequent to formation of a negatively charged adduct with the active site serine residue. Here, we show that membrane patches from liposomes containing NEST, a recombinant hydrophobic polypeptide comprising the esterase domain of human NTE, display a transmembrane ionic conductance with both stable and high-frequency flickering components. An asymmetric current-voltage relationship suggested that ion flow was favoured in one direction relative to the membrane and its associated NEST molecules. Flow of anions was slightly favoured compared with cations. The flickering current formed a much larger proportion of the overall conductance in patches containing wild-type NEST compared with the catalytically inactive S966A mutant form of the protein. The conductance across patches containing NEST, but not those with the S966A mutant, was significantly reduced after adding neuropathic organophosphates to the bathing medium. By contrast, non-neuropathic covalent inhibitors of the catalytic activity of NEST did not reduce NEST-mediated conductance. Future work may establish whether NTE itself mediates an organophosphate-sensitive ion flux across intracellular membranes within intact cells.

Carboxylic Ester Hydrolases↗
PubMed2001

Effect of C1-esterase-inhibitor on capillary leak and inflammatory response syndrome during arterial switch operations in neonates.

OBJECTIVE: To determine if prophylactic administration of C1-esterase-inhibitor would have a beneficial effect on postoperative weight gain and the inflammatory response in neonates undergoing cardiac surgery with cardiopulmonary bypass (CPB). DESIGN: Randomized, double-blinded study. SETTING: University-affiliated heart center. PARTICIPANTS: Twenty-four neonates with transposition of the great arteries. INTERVENTIONS: In group inhibitor (INH) patients (n = 12), 100 IU/kg of C1-esterase-inhibitor (Berinert) was given 30 minutes before CPB. In group placebo (P) patients (n = 12), placebo was administered instead. Interleukin (IL)-6, C3a anaphylatoxin, C1 activity, prekallikrein, Hageman factor, D-dimers, and clinical parameters were measured 6 times perioperatively. MEASUREMENTS AND MAIN RESULTS: All 24 patients had an uneventful clinical course. Mean arterial pressure and pulmonary oxygenation after CPB were superior in group INH patients. The weight gain on postoperative days 1 to 4 was significantly less in group INH patients compared with group P (55 +/- 59 g vs. 340 +/- 121 g, day 1). The concentration of IL-6 (76 +/- 17 pg/mL vs. 262 +/- 95 pg/mL during CPB) was significantly lower in group INH patients compared with group P patients. In contrast, no influence on C3a anaphylatoxin and coagulation factors was found. CONCLUSION: Prophylactic application of C1-esterase-inhibitor in neonates undergoing arterial switch operations produces less inflammatory response compared with placebo. This difference may have contributed to improved clinical parameters, including less weight gain postoperatively.

Capillary Leak Syndrome↗
PubMed1990

Leukocyte esterase activity in amniotic fluid: normal values during pregnancy.

Chorioamnionitis during pregnancy is a common diagnostic dilemma for the obstetrician. Fast and accurate diagnosis poses the most significant problem. Since leukocytes are known to be released in response to infections, examination of amniotic fluid for their presence is an important part of the evaluation for chorioamnionitis. These neutrophils contain several esterases that are not present in serum, urine, or vaginal secretions. The esterases are not influenced by bacteria or by commonly used drugs. We have previously described the reliability of leukocyte esterase (LE) activity for the detection of chorioamnionitis in term pregnancies uncomplicated by other diseases. A prospective study was performed to assess the presence or absence of LE activity to establish normal values in amniotic fluid at various gestational ages prior to term before its use as a possible predictor for chorioamnionitis. Sterile amniotic fluid specimens were obtained from 13 patients undergoing second trimester genetic amniocentesis (with gestational ages varying from 15 to 19 weeks) and from 11 patients with a wide variety of medical problems, undergoing amniocentesis for Rh sensitization or lung maturation studies (with gestational ages ranging from 25 to 27 weeks). All patients with ruptured membranes or preterm labor were excluded. Each amniotic fluid sample was divided into two parts, one of which was transported to the laboratory for aerobic and anaerobic cultures and the other used for LE activity detection as measured by dipstick. The LE results were retrospectively compared with the results of the cultures. LE activity was always found to be negative when the culture results were negative. negative.(ABSTRACT TRUNCATED AT 250 WORDS)

Amniotic Fluid↗
PubMedDate not supplied

Angiooedema due to acquired deficiency of C1-esterase inhibitor associated with leucocytoclastic vasculitis.

A hereditary and an acquired type of C1-esterase inhibitor deficiency have been described. Manifestations characteristic of both forms include recurrent subcutaneous and submucosal angiooedema. Acquired C1-esterase inhibitor deficiency has been observed in association with lymphoproliferative disorders, malignancy, autoimmune diseases and infections. We report on a case with the acquired form of the disease accompanied by leucocytoclastic vasculitis. Treatment with antimalarial agents resulted in complete resolution of symptoms and signs. Furthermore, C1-esterase inhibitor concentration and activity, as well as C1 levels, all returned to normal.

Adult↗
PubMed2004

Ferulic acid: an antioxidant found naturally in plant cell walls and feruloyl esterases involved in its release and their applications.

Ferulic acid is the most abundant hydroxycinnamic acid in the plant world and maize bran with 3.1% (w/w) ferulic acid is one of the most promising sources of this antioxidant. The dehydrodimers of ferulic acid are important structural components in the plant cell wall and serve to enhance its rigidity and strength. Feruloyl esterases are a subclass of the carboxylic acid esterases that hydrolyze the ester bond between hydroxycinnamic acids and sugars present in plant cell walls and they have been isolated from a wide range of microorganisms, when grown on complex substrates such as cereal brans, sugar beet pulp, pectin and xylan. These enzymes perform a function similar to alkali in the deesterification of plant cell wall and differ in their specificities towards the methyl esters of cinnamic acids and ferulolylated oligosaccharides. They act synergistically with xylanases and pectinases and facilitate the access of hydrolases to the backbone of cell wall polymers. The applications of ferulic acid and feruloyl esterase enzymes are many and varied. Ferulic acid obtained from agricultural byproducts is a potential precursor for the production of natural vanillin, due to the lower production cost.

Antioxidants↗
PubMed2001

Microheterogeneous changes of the C1-esterase inhibitor in plasma cannot predict operability, postoperative complications, or recurrence in cancer surgery.

OBJECTIVE: To find out if microheterogeneous changes--such as in molecular weight, isoelectric point, electrophoretic mobility, lectin binding or complexation of the C1-esterase inhibitor--exist in plasma samples from various subgroups of patients. If so, whether these differences could be used diagnostically in single plasma samples from patients with cancer for prognostic assessment of operability or risk of recurrence, and whether any change indicated an increased risk for development of postoperative complications. DESIGN: Retrospective study. SETTING: University hospital, Sweden. SUBJECTS: 16 patients operated on as emergencies for acute peritonitis, 118 patients electively operated on for benign diseases, 274 patients electively operated on for cancer, and 212 patients admitted with acute abdominal pain. MAIN OUTCOME MEASURES: Curative operation, diagnoses, postoperative complications, recurrence of cancer within 2 years. RESULTS: There were no biochemical differences in the C1-esterase inhibitor between single or sequential plasma samples from four large groups of patients with benign disease, cancer, or inflammatory disease, with operable or inoperable cancer, with postoperative complications or not, or with or without early recurrence of cancer. CONCLUSIONS: Specialised biochemical analyses of C1-esterase inhibitor, the most important plasma protease inhibitor of the complement and kinin systems and of contact activation in plasma, cannot be used for prognostic assessment of operability, risk of postoperative complications, or risk of recurrence in patients with cancer.

Abdomen, Acute↗
PubMed2001

Effect of sub-MICs of antimycotics on expression of intracellular esterase of Trichophyton rubrum.

The electrophoretic pattern of the intracellular esterase of the dermatophyte Trichophyton rubrum was altered when this fungus was grown in the presence of subinhibitory concentrations of the antimycotics tioconazole or griseofulvin. All strains (original isolate and antimycotic resistant mutants) presented five clearly visible bands when cultivated on medium containing below-minimum inhibitory concentrations (sub-MICs) of tioconazole or griseofulvin, and only two clearly visible bands when cultivated in medium without antimycotics. No extra bands were detected in the electrophoretic patterns of the extracellular esterase of these fungi (mutants or the original isolate) when cultivated with or without tioconazole or griseofulvin (sub-MIC values). These results suggest that additional forms of esterase are produced inside the cell and may be a nonspecific response to cellular stress, or may participate in cellular detoxification processes in the presence of these antimycotics.

Antifungal Agents↗
PubMed1994

Plasma aspirin esterase activity in elderly patients undergoing elective hip replacement and with fractured neck of femur.

Plasma aspirin esterase activity was measured in eight elderly patients undergoing elective hip replacement, and in 11 presenting with femoral-neck fracture. Elective hip surgery was associated with a marked and significant decline in esterase, from 330 +/- 35.9 (SE) (nmol salicylate/ml plasma/min) pre-operatively to 236 +/- 35.6 on the third post-operative day, and returning to normal (359 +/- 24.3) at recovery phase. Patients with fractured neck of femur showed a depressed esterase activity on admission (221 +/- 12.7), rising towards normal (290 +/- 15.4) on recovery. All of these changes were accompanied by a marked acute-phase response, both to injury and surgery. The data suggest that elderly patients experiencing injury or undergoing surgery may have significantly impaired drug metabolism, at least as far as this enzyme is concerned.

Aged↗
PubMed2003

Recombinant porcine intestinal carboxylesterase: cloning from the pig liver esterase gene by site-directed mutagenesis, functional expression and characterization.

It was shown recently that proline-beta-naphthylamidase from pig liver resembles the gamma-subunit of pig liver esterase (PLE), which could be functionally expressed in the yeast Pichia pastoris in recombinant form (rPLE). The gene encoding rPLE shares 97% identity with the published nucleotide sequence of porcine intestinal carboxylesterase (PICE). By site-directed mutagenesis, 22 nucleotides encoding 17 amino acids were exchanged stepwise from the PLE gene yielding the recombinant PICE sequence and eight intermediate mutants. All esterases were successfully produced in P.pastoris as extracellular proteins with specific activities ranging from 4 to 377 U/mg and V(max)/K(m) values from 12 to 1000 l min(-1) x 10(-3) using p-nitrophenyl acetate as substrate. Activity-staining of native polyacrylamide gels followed by molecular mass determination suggests that the most active forms of all variants are present as trimers with a molecular mass of 190-210 kDa. All enzymes exhibit the highest activity in the pH range 8-9 and between 60 and 70 degrees C. Almost all esterases show a higher ratio of methyl butyrate hydrolase activity to proline-beta-naphthylamidase activity than rPLE.

Amino Acid Sequence↗
PubMed1999

Combined antithrombin III and C1-esterase inhibitor treatment decreases intravascular fibrin deposition and attenuates cardiorespiratory impairment in rabbits exposed to Escherichia coli endotoxin.

OBJECTIVE: To assess the effect of a combined antithrombin III and C1-esterase inhibitor treatment on intravascular organ fibrin deposition and cardiorespiratory changes following intravenous Escherichia coli endotoxin (lipopolysaccharide [LPS] 80 microg/kg i.v.) exposure. DESIGN: Prospective, randomized trial. SETTING: Research laboratory of a university medical center. SUBJECTS: Anesthetized, instrumented and mechanically ventilated rabbits ([Chbb:CH); n = 40). INTERVENTIONS: Endotoxin was given to 30 animals. Ten animals received no inhibitor (endotoxin control group). The other animals were either treated by high-dose (300 units/kg; n = 10) or low-dose (100 units/kg; n = 10) combined antithrombin III and C1-esterase inhibitor administration. Ten rabbits (time control group) were given placebo (sodium chloride 0.9%). Cardiorespiratory variables were assessed at baseline, 120 mins, and 240 mins after endotoxin or placebo administration. Four hours after endotoxin injection, liver, lung, and kidney tissue samples were examined for intravascular fibrin deposition by light microscopy. MEASUREMENTS AND MAIN RESULTS: Inhibitor treatment significantly decreased clot formation in lungs and livers without, however, demonstrating a clear dose-dependent effect. Combined antithrombin III/C1-esterase treatment attenuated the decrease of mean arterial pressure and cardiac output observed following endotoxin injection. Blood pressure improvement was significantly dependent on dosage administered. CONCLUSION: Combination of antithrombin III and C1-esterase inhibitor treatment during early endotoxin shock decreased organ fibrin deposition and improved cardiovascular stability.

Animals↗
PubMed1995

Cyst fluid NB/70K concentration and leukocyte esterase: two new markers for differentiating pancreatic serous tumors from pseudocysts.

Cystic lesions of the pancreas include inflammatory pseudocysts, serous cystadenomas, and mucinous tumors, some of which are malignant. Preoperative clinical and radiological parameters are unreliable and may result in incorrect diagnosis and inappropriate treatment. Cyst fluid analysis for cytology, viscosity, carcino-embryonic antigen, CA 72-4, and CA 15-3 will distinguish mucinous from nonmucinous lesions and usually help in determining malignancy. Currently, there is no reliable method to differentiate inflammatory pseudocysts from serous cystadenomas. This distinction is important because the treatment of these two lesions is different; pseudocysts are either observed or drained, whereas serous tumors are usually resected. The tumor marker NB/70K was measured in aspirated cyst fluid from 13 inflammatory pseudocysts and 11 serous cystadenomas by a commercial immunoassay. Leukocyte esterase was measured using Chemstrip SG urine test strips and amylase and lipase on a routine chemistry analyzer. The cyst fluid NB/70K concentration was significantly higher in pseudocysts (mean, 555 U/ml; range, 42-1,926 U/ml) than in serous cystadenomas (mean, 12 U/ml; range 0-130 U/ml) and this difference was significant (p < 0.0002). Leukocyte esterase was detected in 7 of 11 pseudocysts but was absent in 10 of 10 serous tumors (p = 0.002). Amylase and lipase values were generally higher in pseudocysts but these markers were unreliable due to marked outliers. Cyst fluid NB/70K and leukocyte esterase are promising markers to help differentiate pseudocysts from serous tumors on percutaneous aspirates. When combined with previously reported cyst fluid parameters (amylase, lipase, cytology, and amylase isoenzymes), these two cystic lesions can be reliably distinguished.

Antigens, Neoplasm↗
PubMed1977

Release of Esterase Following Germination of Lettuce Seed (Lactuca sativa L.).

Light-insensitive lettuce seeds, Lactuca sativa L. cv. Great Lakes, release esterases for a period following radicle protrusion. Very little or no enzymes are released prior to 24 hours or after 48 hours of germination. As compared to intact seeds, half-seeds readily release esterases and the release is not affected by far red irradiation. Bulk of the released esterases are derived from the endosperm tissue and presumably exists in the intact seed as a component of the extraembryonic fluid.

Journal Article↗
PubMed1999

X-ray crystallographic determination of the structure of the influenza C virus haemagglutinin-esterase-fusion glycoprotein.

The structure of the haemagglutinin-esterase-fusion (HEF) glycoprotein from influenza C virus has been determined to 3.2 A resolution by X-ray crystallography. A synthetic mercury-containing esterase inhibitor and receptor analogue, 9-acetamidosialic acid alpha-thiomethylmercuryglycoside, was designed as the single isomorphous heavy-atom derivative. The asymmetric unit of one crystal form (form I; P4322, a = b = 155.4, c = 414.4 A) contained an HEF trimer. Six mercury sites identifying the three haemagglutination and three esterase sites were located by difference Patterson map analysis of a 6.5 A resolution derivative data set. These positions defined the molecular threefold-symmetry axis of the HEF trimer. A molecular envelope was defined by averaging a 7.0 A resolution electron-density map, phased by single isomorphous replacement (SIR), about the non-crystallographic threefold-symmetry axis. Iterative non-crystallographic symmetry averaging in real space, solvent flattening and histogram matching were used to extend the phases to 3.5 A resolution. Molecular replacement of the model into a second crystal form (form II; P43212, a = b = 217.4, c = 421.4 A) containing two HEF trimers per asymmetric unit permitted iterative ninefold averaging of the electron density. The 3.5 A electron-density map allowed an unambiguous tracing of the polypeptide chain and identification of N-linked carbohydrates. The model has been refined by least squares to 3.2 A resolution (Rfree = 26.7%).

Acetylesterase↗
PubMed1994

The peach-potato aphid Myzus persicae and the tobacco aphid Myzus nicotianae have the same esterase-based mechanisms of insecticide resistance.

Biochemical and molecular studies have established that in the peach-potato aphid, Myzus persicae, insecticide resistance is conferred by amplification of genes encoding the insecticide-detoxifying esterases E4 or FE4. Here we report that two insecticide-resistant clones of the closely related tobacco aphid Myzus nicotianae have elevated esterases indistinguishable from E4 and FE4 and amplified esterase DNA sequences, and flanking regions, with identical restriction maps to the M. persicae genes. Furthermore, the DNA sequences of c. 630 bp fragments of the E4 and FE4 genes of M. persicae are different from each other but identical to the fragment from corresponding M. nicotianae clones. The existence of apparently identical insecticide resistance genes in the two species can be best explained by the selection of the amplified genes in M. persicae, transfer to hybrids of M. persicae and M. nicotianae by sexual reproduction and subsequent spread through M. nicotianae populations.

Animals↗
PubMed1991

Tryptase in nasal lavage fluid after local allergen challenge. Relationship to histamine levels and TAME-esterase activity.

The activation of mast cells is generally considered to be an important trigger mechanism in the immediate allergic response. This study focused on the determination of three markers of mast cell activation after an allergen challenge. Nasal allergen challenges were performed in 25 subjects with seasonal allergic rhinitis using three allergen doses increasing in 10-fold steps in a standardised nasal lavage model for the subsequent recovery of the markers of mast cell activation. The levels of histamine and tryptase in the nasal lavage fluid were determined using radioimmunoassays, while the TAME-esterase activity was determined using a radiochemical technique. The nasal symptoms obtained on challenge were assessed using a scoring technique. The allergen challenge resulted in significant increases in the levels of all three markers, tryptase, histamine and TAME-esterase. In the individual measurements after the challenges there was a highly significant correlation between the TAME-esterase levels and the tryptase levels (r = 0.71; P less than 0.001), while the generation of histamine and tryptase was not significantly correlated. When comparing the cumulative generation of the three markers, significant correlations were found between all three. Allergen challenges in six non-allergic controls using the same technique did not result in any increase in tryptase levels. The findings suggest that the determination of tryptase in nasal lavage fluid may be a valuable indicator of mast cell activation in the upper airways.

Adult↗
PubMed1989

Purification and molecular properties of rabbit liver esterase ES-1A.

1. The isolation of esterase ES-1A from rabbit liver microsomes/lysosomes is reported. The purification as measured by methylbutyrate-hydrolysing activity, was about 27-fold with a recovery of 2.4%. 2. The resulting product is apparently homogeneous by polyacrylamide (gradient) gel electrophoresis and sodium dodecyl sulphate/polyacrylamide gradient gel electrophoresis after protein staining. The enzyme exhibits heterogeneity after staining for esterase activity and in isoelectric focusing. 3. The molecular mass of the native protein was found to be about 183 kDa (determined by gel filtration and polyacrylamide gel electrophoresis) with a subunit mass of about 63 kDa, indicating a trimeric structure of the enzyme, with subunits of equal size. 4. ES-1A is a glycoprotein and is classified as a carboxylesterase (EC 3.1.1.1). 5. The high degree of similarity of the properties of rabbit ES-1A with those of mouse ES-6A and rat ES-10 suggests that these three esterases may have a common evolutionary origin.

Animals↗