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Enzyme-catalysed conjugations of glutathione with unsaturated compounds.

ABSTRACT: 1. Rat-liver supernatant catalyses the reaction of diethyl maleate with glutathione. 2. Evidence is presented that the enzyme involved is different from the known glutathione-conjugating enzymes, glutathione S-alkyltransferase, S-aryltransferase and S-epoxidetransferase. 3. Rat-liver supernatant catalyses the reaction of a number of other alphabeta-unsaturated compounds, including aldehydes, ketones, lactones, nitriles and nitro compounds, with glutathione: separate enzymes may be responsible for these reactions.

SUBMITTER: Boyland E

PROVIDER: S-EPMC1270549 | biostudies-other | 1967 Jul

REPOSITORIES: biostudies-other

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Enzymes catalysing conjugations of glutathione with alpha-beta-unsaturated carbonyl compounds.

Project description:1. Heat-inactivation experiments, ammonium sulphate-fractionation studies, enzyme-inhibition studies with S-(alphabeta-diethoxycarbonylethyl)glutathione, and evidence from the distribution of activities in rat liver, in rat kidney and in the livers of other animals, indicate that reactions of glutathione with (i) trans-benzylideneacetone, (ii) cyclohex-2-en-1-one, (iii) trans-cinnamaldehyde, (iv) diethyl maleate, (v) diethyl fumarate and (vi) 2,3-dimethyl-4-(2-methylenebutyryl)phenoxyacetic acid are catalysed by different enzymes. 2. Evidence is presented that the enzymes catalysing the reactions of glutathione with substrates (i)-(iv) are different from glutathione S-alkyltransferase, S-aryltransferase and S-epoxidetransferase. 3. The name ;glutathione S-alkenetransferases' is proposed for enzymes catalysing reactions of glutathione with alphabeta-unsaturated compounds. 4. The Arrenhius plot for the enzyme-catalysed reaction of diethyl maleate with glutathione is discontinuous, with lower energy of activation at 38 degrees .

| S-EPMC1186951 | biostudies-other

Distribution of enzymes that catalyse reactions of glutathione with alpha beta-unsaturated compounds.

Project description:1. A study of the distribution of glutathione S-alkenetransferases in the livers of vertebrate species suggests that different enzymes may catalyse reactions of GSH with (i) trans-benzylideneacetone, (ii) 2,3-dimethyl-4(2-methylenebutyryl)phenoxyacetic acid, (iii) cinnamonitrile, (iv) o-chlorobenzylidenemalononitrile, (v) methyl vinyl sulphone, and (vi) 3-(beta-nitrovinyl)indole. 2. Glutathione S-alkenetransferase activity was generally greatest in rat liver, but the enzyme in hamster liver was more active towards o-chlorobenzylidenemalononitrile, and the enzyme in rabbit, hamster, guinea-pig and mouse livers was more active towards methyl vinyl sulphone. 3. Results from studies of the distribution of activities in rat liver and rat kidney, heat inactivation of rat liver supernatants, and (NH(4))(2)SO(4) fractionation and acid-precipitation experiments, differentiated further between some of the enzymes concerned with substrates (i)-(vi). 4. The infrequent detection of mercapturic acids in vivo is discussed.

| S-EPMC1177536 | biostudies-other

Fe(OTf)3-catalysed Friedel-Crafts reaction of benzenoid arenes with α,β-unsaturated carbonyl compounds: easy access to 1,1-diarylalkanes.

Project description:A simple and efficient method for the synthesis of 1,1-diarylalkanes via the Friedel-Crafts-type alkylation reaction of electron-rich arenes with cinnamic acid ester derivatives or chalcones is reported. Iron triflate has been found to be the best catalyst for the Friedel-Crafts-type alkylation reaction with α,β-unsaturated carbonyl compounds. This reaction afforded β,β-diaryl carbonyl compounds in good yields (65-93%) and with excellent regioselectivities. Remarkably, this method is also compatible with a variety of indoles to provide 3-indolyl-aryl carbonyl compounds in excellent yields. Great efforts have been made to deduce a plausible reaction mechanism based on isotopic labelling experiments.

| S-EPMC5666261 | biostudies-literature

Unusual C=C bond isomerization of an α,β-unsaturated γ-butyrolactone catalysed by flavoproteins from the old yellow enzyme family.

Project description:An unexpected, redox-neutral C=C bond isomerization of a γ-butyrolactone bearing an exo-methylene unit to the thermodynamically more favoured endo isomer (k(cat) =0.076 s(-1) ) catalysed by flavoproteins from the Old Yellow Enzyme family was discovered. Theoretical calculations and kinetic data support a mechanism through which the isomerization proceeds through FMN-mediated hydride addition onto exo-Cβ, followed by hydride abstraction from endo-Cβ', which is in line with the well-established C=C bond bioreduction of OYEs. This new isomerase activity enriches the catalytic versatility of ene-reductases.

| S-EPMC3533789 | biostudies-literature

Bi(OTf)<sub>3</sub>-catalysed intramolecular cyclisation of unsaturated acetals.

Project description:A series of highly functionalized carbocycles was efficiently prepared via the selective cyclisation of unsaturated acetals and ketals in the presence of only 1 mol% of Bi(iii) or Fe(iii) triflates as the catalysts at room temperature, with yields ranging from 60 to 90%. With Bi(OTf)3 catalysis, α,β-unsaturated ether carbocycles are formed selectively, whereas with the Fe(OTf)3 system, a cycloisomerisation to carbocyclic diethers is mainly obtained. This acetal/olefin cyclisation could be run at a multi-gram scale and compound 2c could be obtained on a 300 gram-scale with a yield of 69% after precipitation in hexane.

| S-EPMC9034051 | biostudies-literature

The Methyl Torsion in Unsaturated Compounds.

Project description:How the methyl torsion transition energy in unsaturated systems is affected by its environment is investigated. It is strongly influenced by both its immediate neighborhood, (the number of methyl groups present in the molecule) and the intermolecular interactions. It is clear that the intermolecular interactions have a major influence on the torsion transition energy, as demonstrated unambiguously previously for mesitylene and also seen here for other systems. In part, this may be caused by the fact that the methyl torsion is rarely a pure mode (unless enforced by symmetry). Where the crystal structure is available, the assignments have been supported by CASTEP calculations of the unit cell. The agreement between the observed and calculated spectra is generally good, although not perfect, toluene being a case in point, and highlights just how demanding it is to obtain accurate transition energies for low energy modes. The disagreement between observed and calculated inelastic neutron scattering spectra for meta-xylene and 9,10 dimethylanthracene is so severe that it would suggest that there are additional phases to those presently known. Comparison between the full periodic calculations and those for the isolated molecule shows that intermolecular interactions raise the methyl torsion transition energy by at least 8% and in some cases by more than 50%. The presence of more than one methyl group in the molecule generally raises the average torsion energy from the <100 cm-1 seen for single methyl groups to 150-200 cm-1.

| S-EPMC7033956 | biostudies-literature

Enzyme-catalysed reactions between some 2-substituted 5-nitrofuran derivatives and glutathione.

Project description:1. A glutathione transferase present in rat and human liver supernatant catalyses the reaction of some 2-substituted 5-nitrofuran derivatives with GSH, with formation of a conjugate and release of the nitro group as inorganic nitrite. Some of the substrates undergo the same reaction at a slower rate in the absence of enzyme. Nitrofuran derivatives commonly used as drugs, and five other drugs containing nitro groups, did not react. 2. Substrate activity in the nitrofuran derivatives showed an approximate correlation with the lability of the nitro group to alkali. 3. Optimum pH values ranging from 6.6 to 9.0 were found for the enzymic reaction with various derivatives, the values being influenced by alkali-lability and pK values of the compounds. 4. Tenfold purification of rat liver glutathione S-aryl-transferase resulted in an equal purification of the activities that catalyse the reaction of two of the nitrofuran derivatives with GSH.

| S-EPMC1179375 | biostudies-other

Cloning and heterologous expression of cDNA encoding class alpha rat glutathione transferase 8-8, an enzyme with high catalytic activity towards genotoxic alpha,beta-unsaturated carbonyl compounds.

Project description:A cDNA clone, lambda GTRA8, encoding rat glutathione transferase subunit 8 has been isolated from a lambda gt10 rat hepatoma cDNA library. The previously known amino acid sequence of the enzyme was used to design primers for a polymerase chain reaction that yielded a 0.3 kb DNA fragment from the hepatoma library. The 0.3 kb fragment was used as a probe for screening and a 0.9 kb cDNA clone containing a complete open reading frame was obtained. After DNA sequencing and subcloning into an expression vector, the enzyme was expressed in Escherichia coli and purified. Specific activities and kcat./Km values were determined for a number of substrates, including alpha,beta-unsaturated carbonyl compounds. The highest activity was obtained with 4-hydroxyalkenals and with acrolein, genotoxic products of lipid peroxidation. In addition, the rat class Alpha glutathione transferase 8-8 displays high catalytic activity in the reaction between glutathione and the diuretic drug ethacrynic acid, a compound normally considered as a substrate characteristic for class Pi glutathione transferases.

| S-EPMC1132639 | biostudies-other

Isothiourea-catalysed enantioselective Michael addition of N-heterocyclic pronucleophiles to α,β-unsaturated aryl esters.

Project description:The isothiourea-catalysed enantioselective Michael addition of 3-aryloxindole and 4-substituted-dihydropyrazol-3-one pronucleophiles to α,β-unsaturated p-nitrophenyl esters is reported. This process generates products containing two contiguous stereocentres, one quaternary, in good yields and excellent enantioselectivities (>30 examples, up to > 95 : 5 dr and 99 : 1 er). This protocol harnesses the multifunctional ability of p-nitrophenoxide to promote effective catalysis. In contrast to previous methodologies using tertiary amine Lewis bases, in which the pronucleophile was used as the solvent, this work allows bespoke pronucleophiles to be used in stoichiometric quantities.

| S-EPMC8133005 | biostudies-literature

Iron-catalysed cross-coupling of organolithium compounds with organic halides.

Project description:In past decades, catalytic cross-coupling reactions between organic halides and organometallic reagents to construct carbon-carbon bond have achieved a tremendous progress. However, organolithium reagents have rarely been used in cross-coupling reactions, due mainly to their high reactivity. Another limitation of this transformation using organolithium reagents is how to control reactivity with excellent selectivity. Although palladium catalysis has been applied in this field recently, the development of an approach to replace catalytic systems of noble metals with nonprecious metals is currently in high demand. Herein, we report an efficient synthetic protocol involving iron-catalysed cross-coupling reactions employing organolithium compounds as key coupling partners to unite aryl, alkyl and benzyl fragments and also disclose an efficient iron-catalysed release-capture ethylene coupling with isopropyllithium.

| S-EPMC4748252 | biostudies-literature

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