P-nitrophenol Esters Research Articles

Synthetic catalytic polymers containing oxime groups: Effect of substrate structure on esterolysis of p-nitrophenyl esters

The catalytic activity of different polymers containing axime groups has been tested in the hydrolysis of structurally different esters of p-nitrophenol. The mechanism of hydrolysis, supported by indirect kinetic evidence, seems not to involve a pre-equilibrium with a polymer-ester complex. The reaction was investigated under pseudo-first-order conditions with an excess of oxime polymer. The values of the second-order catalytic rate coefficients suggest a reaction rate mainly controlled by steric effects and hydrophobic interaction between the ester hydrocarbon residue and the macromolecular chain.

The phospholipase A1 of Trypanosoma brucei does not release myristate from the variant surface glycoprotein.

[3H]Myristoyl-labeled variant surface glycoprotein (VSG) has been isolated from Trypanosoma brucei by reverse phase high performance liquid chromatography and used as substrate for the conversion by trypanosomal enzymes of membrane-form VSG to soluble VSG. Conversion is detected by the release of myristoyl-containing lipids. The major lipolytic enzyme of T. brucei, phospholipase A1, is effective for the hydrolysis of myristoyl esters of p-nitrophenol, in a colorimetric assay. However, the phospholipase is unable to cleave the myristoyl ester linkage of VSG. The phospholipase can be separated from the myristoyl-releasing activity of trypanosome homogenate by centrifugation, affinity chromatography, and anion-exchange chromatography. Elution profiles on anion-exchange high performance liquid chromatography also indicate that the phospholipase is inactive against VSG. A small amount of myristoyl-releasing activity associated with the purified phospholipase is probably due to contamination with a phosphodiesterase which releases myristoyl-containing diglyceride from VSG.

Catalytic esterolysis of p-nitrophenyl esters by optically active polymeric oximes

An optically active polymer containing oxime groups was prepared by partial quaternization of a copolymer of 4-vinyl pyridine and (+)(S)-4-methyl-1-hexen-3-one, with phenacyl bromide and subsequent reaction with hydroxylamine hydrochloride. This polymer was used as a catalyst for the esterolysis of esters of p-nitrophenol with aliphatic and aromatic carboxylic acids characterized by different steric and hydrophobic features. The detailed evaluation of kinetic parameters permitted identification of the main factors responsible for the catalytic behaviour.

Trypanosoma cruzi: Carboxylesterase activity in intact epimastigotes

1. 1. Carboxylesterase activity corresponding to types A and B has been demonstrated in intact T. cruzi epimastigotes as shown by the hydrolysis of several esters of p-nitrophenol and the effect of suitable inhibitors. 2. 2. The in situ carboxylesterase activity was described by the Michaelis-Menten kinetic approach. The apparent V max for the acetate and butyrate esters were 66.5 and 165.3 nmol hydrolysed per min and mg of protein respectively. 3. 3. An Arrhenius plot of the temperature dependent activity showed two sharp linear regions with a transition temperature of 31.6°C and energies of activation of 6.2 and 14.1 kcal/mol. 4. 4. The in situ carboxylesterase activity was inhibited 26% by paraoxon and 56% by N-ethylmaleimide, but not by p-chloromercuribenzoate.

Catalytic hydrolysis of esters of p-nitrophenol bound by amylose in the dimethyl sulfoxide-water mixed-solvent system

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTCatalytic hydrolysis of esters of p-nitrophenol bound by amylose in the dimethyl sulfoxide-water mixed-solvent systemYongzheng Hui, Shujing Wang, and Kikui JiangCite this: J. Am. Chem. Soc. 1982, 104, 1, 347–349Publication Date (Print):January 1, 1982Publication History Published online1 May 2002Published inissue 1 January 1982https://doi.org/10.1021/ja00365a088RIGHTS & PERMISSIONSArticle Views101Altmetric-Citations21LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (395 KB) Get e-Alerts Get e-Alerts

Synthesis and catalytic activity of optically active polymers containing oxime groups

Optically active polymers containing oxime groups have been prepared: (i) by partial quaternization of poly(4-vinyl pyridine) (P4VP) with phenacyloxime bromide and with (+)-(S)-1-bromo-2-methylbutane; and (ii) by reaction of the copolymer from 4VP and (+)-(S)-5-methyl-1-hepten-3-one with hydroxylamine. These polymers have been used as catalysts for the esterolysis of esters of p-nitrophenol with non-chiral and with chiral acids. The kinetic parameters of the catalytic process are markedly dependent on the structure of polymer and substrate. A moderate chiral discrimination of the antipodes of p-nitrophenyl 2-methylbutanoate is observed with the catalyst obtained from the copolymer of 4VP with (+)-(S)-5-methyl-1-hepten-3-one.

Transient-phase and steady-state kinetics of lipase-catalyzed ester hydrolysis.

An experimental study has been made of both the steady-state and the transient-phase (presteady-state) kinetics of the hydrolyses of several saturated aliphatic esters of p-nitrophenol catalyzed by wheat germ lipase. The analysis of the presteady- 1 Presented in part at the 173rd ACS National Meeting, New Orleans, L.A., U.S.A., March 20--25, 1977. 2 Correspondence should be addressed to M.H. Sadar, E.S.D., E.H.C., Health and Welfare Canada, Tunney's Pasture, Ottawa, Ontario, Canada, K1A OL2. 3 Department of Chemistry, University of Ottawa, Ottawa, Ontario, Canada. state part revealed two transients indicating that lipase-catalyzed reactions proceed via a two-intermediate mechanism suggested for other esterases. The possibility of more than one species of the enzyme engaged in catalytic activity is discussed and a reaction mechanism scheme is proposed accordingly.

Transient‐phase and steady‐state kinetics of lipase‐catalyzed ester hydrolysis1

An experimental study has been made of both the steady-state and the transient-phase (presteady-state) kinetics of the hydrolyses of several saturated aliphatic esters of p-nitrophenol catalyzed by wheat germ lipase. The analysis of the presteady- 1 Presented in part at the 173rd ACS National Meeting, New Orleans, L.A., U.S.A., March 20--25, 1977. 2 Correspondence should be addressed to M.H. Sadar, E.S.D., E.H.C., Health and Welfare Canada, Tunney's Pasture, Ottawa, Ontario, Canada, K1A OL2. 3 Department of Chemistry, University of Ottawa, Ottawa, Ontario, Canada. state part revealed two transients indicating that lipase-catalyzed reactions proceed via a two-intermediate mechanism suggested for other esterases. The possibility of more than one species of the enzyme engaged in catalytic activity is discussed and a reaction mechanism scheme is proposed accordingly.

Active esters in the formation of ester bonds between amino acids and polymeric supports.

The imidazole catalyzed transesterification of active esters was used for the formation of the ester bond between the carboxyl group of protected amino acids and the hydroxyl group of a polymeric support applied in solid phase peptide synthesis. Anchoring of the C-terminal residue to the hydroxymethyl polymer proceeded smoothyl and provided a high degree of incorporation. No racemization was observed in the imidazole-catalyzed alcholysis. The procedure could be carried out with various active esters such as esters of o-and p-nitrophenol, 2,4,5-trichlorophenol, pentachlorophenol and N-hydroxysuccinimide.

The effect of temperature on the individual stages of the hydrolysis of non-specific-p-nitrophenol esters by alpha-chymotrypsin.

Precise studies were performed on the effect of temperature on the rate and equilibrium parameters characterizing the individual stages of the alpha-chymotrypsin-catalysed hydrolysis of non-specific p-nitrophenol esters at pH 7.40 and 8.50. At both pH values the results indicate that a sharp kinetic anomaly is observed in Arrhenius plots of these parameters for the binding and acylation stages of the process, but not for the deacylation stage. Detailed comparison with other kinetic studies was made, and a comparison with thermal transitions observed in alpha-chymotrypsin by using physical techniques was attempted. A detailed discussion of possible causes of the anomalies is given.

Characterization of canine hepatic and renal esterases.

The esterases of canine liver and kidney were separated electrophoretically into nine bands with identical migration patterns in both tissues. An additional pair of rapidly migrating anodic bands were observed in hepatic extracts. Based on substrate specificity, the predominant tissue esterases were identified as nonspecific carboxylesterases (aliesterases). No cholinesterase activity was detected in the tissue extracts. Kinetic characteristics determined for the hepatic and renal esterases included (1) optimal pH; (2) Km values for esters of α-naphthyl and p-nitrophenol; (3) average rates of hydrolysis of α-naphthyl acetate and p-nitrophenyl acetate by the tissue extracts. Inhibition studies revealed the presence of two types of esterase activity in each tissue: one type being sensitive to organophosphorus esters, the second being resistant. A study of preferential substrate hydrolysis in the presence of known characteristic activators and inhibitors of esterases revealed approximately 5% and 20% arylesterase activity in liver and kidney, respectively. The presence of arylesterase activity in these tissues was confirmed by the hydrolysis of paraoxon (E600).

Characterization of the esterases of canine serum.

Various techniques including electrophoresis, gel filtration, and titrimetric and spectrophotometric analysis with specific and nonspecific substrates and inhibitors were used to characterize the serum esterases of male and female dogs. Electrophoresis in starch gel yielded 10 distinct bands of activity: four butyrylcholinesterase bands, an esterolytically active albumin, and five bands of aliesterase and/or arylesterase activity. Gel filtration on Sephadex G-200 yielded two distinct peaks of activity, one containing the cholinesterase bands, and the second peak containing both arylesterase and aliesterase activity in close association with the serum albumin. Kinetic characteristics determined for the canine serum esterases included (1) optimal pH; (2) Km values for esters of choline, α-naphthol, and p-nitrophenol; and (3) average rates of hydrolysis of α-naphthyl acetate, butyrylcholine iodide, p-nitrophenyl acetate, and E600 by the sera of males and females. The sensitivity of the serum esterases to inhibition by various cations, and specific and nonspecific inhibitors was investigated. The organophosphate, E600, may be a highly specific substrate for the detection and quantification of arylesterase in a mixture of nonspecific carboxylesterases.

Deficiency of acid esterase activity in Wolman's disease.

Liver, spleen, and leucocytes from patients with acid triglyceride lipase deficiency (Wolman9s disease and its clinical variants) were also found to possess greatly reduced activity of an acid esterase acting on fatty acid esters of p-nitrophenol, thereby substantiating the view that a single enzyme is responsible for these different activities. The acid esterase was resistant to the microsomal esterase inhibitor, E600, and showed broad specificity with respect to fatty acid chain length of the p-nitrophenyl esters. Other lysosomal hydrolase activities were increased non-specifically in liver from patients, thus providing further support for the classification of acid lipase deficiency as an inborn lysosomal disease. The highly sensitive leucocyte assay provides a convenient method for the diagnosis of clinical variants of Wolman9s disease; it might therefore prove particularly useful in the early detection of affected infants, and also possibly in the differentiation of heterozygotes.

Hydrolysis of higher fatty acid esters of p-Nitrophenol by rat liver and kidney lysosomes

Esterases, acting on higher fatty acid esters of p-nitrophenol, are shown to be concentrated in the lysosomes of rat liver and kidney by the amount of enzyme sedimented with light mitochondria, by the purification of lysosomes, and by the preparation of Triton WR 1339-filled liver lysosomes. Most of the esterase of liver lysosomes is associated with the lysosomal membrane, whereas a major portion of the kidney lysosomal esterase can be solubilized by freezing and thawing. The pH optimum of the lysosomal esterase of both tissues is between 3.6 and 4. The K m of liver lysosomal esterase for p-nitrophenyl myristate is 0.001 m. The lysosomal esterase is activated by Triton X-100, inhibited by citrate, phthalate, NaCl, EDTA, protamine sulfate, Hg ++, iodoacetate, NaF, deoxycholate, and taurocholate. The esterase is unaffected by 10 −4 m DFP, bovine serum albumin, Triton WR 1339, and most divalent cations. The microsomal esterase of both tissues is powerfully inhibited by 10 −4 m DFP. The relative rates of hydrolysis of p-nitrophenyl esters containing from 8 to 18 carbon atoms in the fatty acid were determined. The lysosomal esterases are least active on p-nitrophenyl caprylate and more active on higher fatty acid esters. The microsomal esterase is most active on p-nitrophenyl caprylate and has very little activity on higher fatty acid esters. The properties of lysosomal acid esterase and acid lipase are discussed.

Properties of steroid sulphatase and arylsulphatase activities of human placenta.

1. The properties of enzyme activities hydrolysing the sulphate esters of dehydroepiandrosterone, oestrone and p-nitrophenol are reported. The preparation studied was obtained from the microsomal fraction of human placenta by ultrasonic treatment and addition of Triton X-100. 2. The behaviour of the preparation during sedimentation at 105000g and attempts at purification indicated that the activities were particulate. Electron microscopy demonstrated the rupture of vesicular structures approx. 0.5mu in diameter concurrent with the release of activity. 3. The three activities were always associated throughout repeated attempts at separation by sucrose-density-gradient centrifugation and Sephadex-gel filtration. On the basis of kinetic studies, stability studies and treatment with butanol and ribonuclease it was concluded that a separate enzyme is responsible for each of the three activities. Widely varying plots of activity as a function of pH were consistent with this conclusion. 4. On the basis of sensitivity of the enzymes hydrolysing dehydroepiandrosterone sulphate and oestrone sulphate to ribonuclease and sensitivity of all three enzymes to lipase, it was concluded that the three enzymes are bound to a particle containing lipid and RNA. Enzymic activity is dependent on structural integrity of the particle. 5. A spectrophotometric method for the assay of oestrone sulphate hydrolysis is described. 6. Hydrolysis of nitrocatechol sulphate by human placenta under conditions described for arylsulphatases A and B is reported.

Steric Effects in the Hydrolysis of N-Acylimidazoles and Esters of p-Nitrophenol

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTSteric Effects in the Hydrolysis of N-Acylimidazoles and Esters of p-NitrophenolThomas H. FifeCite this: J. Am. Chem. Soc. 1965, 87, 20, 4597–4600Publication Date (Print):October 1, 1965Publication History Published online1 May 2002Published inissue 1 October 1965https://doi.org/10.1021/ja00948a035RIGHTS & PERMISSIONSArticle Views262Altmetric-Citations40LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (501 KB) Get e-Alerts Get e-Alerts

Enzymatic sulfation of steroids by bovine tissues

The synthesis of sulfate esters of dehydroepiandrosterone (DHA), estrone, testosterone, and p-nitrophenol by the supernatant fraction of various adult bovine tissue homogenates is reported. All tissues synthesized p-nitrophenyl sulfate. Synthesis of testosterone sulfate occurred only with liver. Estrone sulfate was formed by many tissues, but synthesis of DHA sulfate was limited to placenta, liver, adrenal gland, intestine, pituitary, kidney, and uterus. Bovine placenta was much more active than human placenta in the sulfation of these substrates.

ESTERASES OF TESTIS AND OTHER TISSUES

The tissues most effective in the enzymatic hydrolysis of acyl esters of p-nitrophenol by tissue extracts of the rat and dog were the liver, lung, pancreas, renal cortex, and testis; in the dog tracheal and vesical mucosae were also esterase-rich and the lens had appreciable activity. Esterase was at low concentration in the tissues of the rat for 4 and 5 days after birth, but an increase to adult levels soon took place except in the testis where the rise was delayed until puberty. The esterase values of the blood of newborn children were also low. Two patterns of activity in tissues against these esters were found. A pattern in which propionate esters were hydrolyzed most rapidly was displayed regularly by liver, lung, renal cortex, and testis of the rat and also by dog, rabbit and human serum. A second pattern with progressive effectiveness in hydrolyzing fatty acid esters of 2-carbon to 5-carbon chain length was exhibited by the pancreas of the rat, rabbit, and dog and also by rat serum. Esterase of the testis of the rat is located in the interstitial cells and its concentration seems to be directly related to androgenic hormone production. The increase of testicular esterase during puberty paralleled the increase of prostatic weight. Hypophysectomy caused a profound decrease of testicular esterase which was restored in part by gonadoptrophin. Artificial cryptorchism in the rat, causing elimination of germinal epithelium, resulted in an increase of esterase concentration although the total content of the testis slowly decreased.