Esterase

About: Esterase is a research topic. Over the lifetime, 7622 publications have been published within this topic receiving 168270 citations.

Biochemical demonstration of the activatable esterase of the rabbit netrophil involved in the chemotactic response.

Abstract: Direct biochemical evidence is provided that the rabbit blood neutrophil contains a precursor esterase involved in the cell response to the chemotactic stimulus C567, and that contact of the cell with chemotactic factor leads to activation of the proesterase. Rabbit blood leukocytes contain esterase 1, that is, an enzyme capable of hydrolyzing acetyl-dl-phenylalanine β-naphthyl ester. This activity can be ascribed largely, if not entirely, to the presence of neutrophils. Comparing blood leukocytes with peritoneal (exudate) neutrophils, the former cells contain greater esterase activity as well as greater chemotactic responsiveness. Treatment of blood leukocytes, but not peritoneal neutrophils, with chemotactic factor results in the acquisition of esterase activity (“esterase activation”) and chemotactic deactivation (loss of chemotactic responsiveness). By using highly purified complement and preparative (density gradient) ultracentrifugation, and employing agents that dissociate the macromolecular chemotactic factor, the phenomena of chemotactic activity, esterase-activating capacity and deactivating potential have been shown to be interrelated and clearly ascribable to C567. The esterase that appears in the blood leukocyte as a result of interaction with C567 can be identified as esterase 1, on the basis of exquisite sensitivity to inhibitory effects of phosphonate compounds at very low concentrations (10-8 M). These data provide direct biochemical support for the original hypothesis that the chemotactic response of the neutrophil to the complement chemotactic factor C567 involves an interaction which results in the conversion of the cell-bound proesterase to an active esterase. The biochemical role of this esterase in the kinetic behavior of the granulocyte is not known. This information may have special relevance to at least four other phenomena in which activation of a protesterase to an active esterase as the cause of an “allergic response” has been postulated on the basis of indirect evidence.

Biochemical and functional properties of serine esterases in acidic cytoplasmic granules of cytotoxic T lymphocytes.

Abstract: Percoll gradient fractions of homogenates of murine cloned cytotoxic T lymphocytes (CTL) were analyzed for the trypsin-like enzyme alpha-N-benzyloxy-carbonyl-L-lysinethiobenzyl ester (BLT) esterase recently described in CTL homogenates. Enzymatic activity was found in three areas of the gradient: the dense cytolysin containing granules; a light granule fraction; and a variable amount in the soluble fraction at the top of the gradient. Gel filtration columns showed a major peak of BLT esterase activity eluted at the position of a 60-kDa protein, and an additional, minor BLT esterase peak eluting at about 27 kDa. The separated enzymes were both significantly inhibited by the serine protease inhibitors diisopropylfluorophosphate and phenylmethyl sulfonyl fluoride (PMSF), indicating they are both serine proteases, but showed different patterns of inhibition by a series of inhibitors, suggesting the larger enzyme is not a simple dimer of the smaller. pH activity profiles of both CTL BLT esterases showed an optimum at about pH 8. PMSF inactivation of BLT esterase in detergent extracts of CTL diminished sharply as the pH was dropped below 7. Agents which raise the pH of acidic intracellular compartments were found to markedly enhance the PMSF inactivation of BLT esterase in intact CTL, showing that the granules have a low internal pH. Similarly, [3H]diisopropylfluorophosphate labeling of intact CTL gave four protein bands on non-reduced gels, of which two were labeled threefold more effectively in the presence of chloroquine. In parallel studies of inactivation of CTL lytic activity, PMSF pretreatment caused a 50% reduction of the lytic activity under conditions where greater than 90% of the BLT esterase activity was inactivated. Addition of agents raising the intragranular pH dramatically enhanced the BLT esterase inactivation but did not concomitantly reduce CTL lytic activity. These results indicate that inactivation of lytic function by PMSF is unlikely to be due to its reaction with protease in acidic granules, and suggest that the activity of these enzymes may not be required for cytotoxicity.

Bioreversible protection for the phospho group: bioactivation of the di(4-acyloxybenzyl) and mono(4-acyloxybenzyl) phosphoesters of methylphosphonate and phosphonoacetate

Abstract: The di(4-acetoxybenzyl) ester of methylphosphonate 4(X = H, R = Me) and the di(4-acyloxybenzyl) esters of methoxycarbonylmethylphosphonate 4(X = MeO2C, R = Me, Et, Pr, Pri, Bu or But) were prepared from the appropriate benzyl alcohol and phosphonic dichloride. At pD 8.0 and 37 °C, both series of compounds hydrolyse with half-lives greater than 24 h to the corresponding mono(4-acyloxybenzyl) esters 5(X = H or MeO2C, R = Me, Et, Pr, Pri Bu or But) which were prepared by treatment of the di(4-acyloxybenzyl) esters 4 with sodium or lithium iodide. The mono(4-acyloxybenzyl) esters 5(X = H, R = Me) and 5(X = MeO2C, R = Me, Et, Pr, Pri or But) undergo chemical hydrolysis to methylphosphonate 6(X = H), and methoxycarbonylmethylphosphonate 6(X = MeO2C) respectively, together with 4-hydroxybenzyl alcohol and the appropriate acylate anion. The rates of hydrolysis of the mono(4-acyloxybenzyl) esters decrease as the length and steric bulk of the acyl group increases, with half-lives ranging from ∼ 150 h for the acetyl analogues to 2240 h for the pivaloyl derivative. The hydrolyses of the di- and mono-(4-acyloxybenzyl) esters were catalysed by porcine liver carboxyesterase (PLCE), and in all cases the acylate anion was formed. The rate of enzymatic hydrolysis was most rapid for the 4-butanoyloxybenzyl and 4-isobutanoyloxybenzyl analogues. The methoxycarbonyl ester of the phosphonoacetate analogues was not cleaved by PLCE. The methylphosphonate generated from the reaction of 4(X = H, R = Me) in the presence of esterase and H218O, did not contain 18O attached directly to phosphorus. These results suggest that both the chemical and enzymatic hydrolyses of the mono(4-acyloxybenzyl) esters and the PLCE-catalysed hydrolyses of the di(4-acyloxybenzyl) esters proceed via hydrolysis of the acyl group to give the acylate anion and the unstable 4-hydroxybenzyl esters. The electron-donating 4-hydroxy group facilitates the cleavage of the benzyl-oxygen bond with the formation of the 4-hydroxybenzyl carbonium ion 9, which readily reacts either with water or the phosphate buffer. The 4-acyloxybenzyl phosphoesters provide the first example of a protecting group which will enable the bioactivation of phosphonate prodrugs at rates appropriate to biological systems.

Enhanced degradation of an endocrine-disrupting chemical, butyl benzyl phthalate, by Fusarium oxysporum f. sp. pisi cutinase.

Abstract: Compared to yeast esterase, fungal cutinase degraded butyl benzyl phthalate (BBP) far more efficiently; i.e., almost 60% of the BBP disappeared within 7.5 h. Also, the final chemical composition significantly depended on the enzyme used. Toxicity monitoring using bioluminescent bacteria showed that butyl methyl phthalate, a major product of degradation by esterase, was an oxidative toxic hazard.

Studies on enzymatic histochemistry : xxv. a micro method for the determination of choline esterase and the activity-ph relationship of this enzyme.

Abstract: The activity-pH relationship for choline esterase from horse serum, gastric mucosa of the pig, and cat brain was investigated, and an optimum was observed at pH 8.5 in each case. A micro method for the determination of choline esterase was developed capable of measuring the hydrolysis down to the order of that given by 1 x 10–8 mol of ester.