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PubMed1975

Specific inhibition of sclerotium formation by 2-mercaptoethanol and related sulfhydryl compounds in Sclerotium rolfsii.

Sclerotium formation in Sclerotium rolfsii was completely inhibited by 2-mercaptoethanol at a concentration of 2-4 mM without any adverse effect on mycelial growth. Concentrations lower than 2 mM had no effect on mycelial growth and sclerotium formation, whereas both were inhibited at concentrations higher than 4 mM. Complete inhibition of sclerotium formation with no effect on mycelial growth was also obtained by propyl mercaptan, 1-butyl mercaptan and 2-butyl mercaptan at a concentration of 0.10 mM. Sclerotium formation was also inhibited by benzyl mercaptan and thioglycolic acid at 0.15 mM and 2-4 mM concentration respectively, whereas it was only partially inhibited by L-cysteine and glutathione at 20 mM. Mycelium grown for 21 days in nutrient medium supplemented with mercaptoethanol at a concentration of 3 mM, when transferred into fresh medium without the chemical, grew normally and produced abundant mature sclerotia. Mercaptoethanol inhibited the initiation as well as the further development of young, unpigmented sclerotia. The mechanism of sclerotium formation was arrested completely when mercaptoethanol was added to the growth medium at any time between inoculation and the appearance of sclerotia of the "development" stage. It is suggested that the specific inhibitory action of mercaptoethanol could be used to study the mechanism of sclerotium formation

Cysteine↗

PubMed1983

Comparison of the 2-mercaptoethanol and dithiothreitol tests for determining Brucella immunoglobulin G agglutinating antibody in bovine serum.

The dithiothreitol test was evaluated as a substitute for the 2-mercaptoethanol test for determining Brucella immunoglobulin G agglutinating antibody in bovine serum. The tests were compared on 207 card-positive sera that showed a standard tube-agglutination titer of incomplete 1:50 or higher. The tests agreed within one dilution with 182 of the 207 sera tested for an 87.9% rate of agreement. When titers were not the same, those obtained with the dithiothreitol test were more frequently lower than higher than those obtained with the 2-mercaptoethanol test. Sixteen sera that showed a titer with the 2-mercaptoethanol test were negative with the dithiothreitol test and two that showed a titer with the dithiothreitol test were negative with the 2-mercaptoethanol test. Results suggest that the dithiothreitol test is not a reliable substitute for the 2-mercaptoethanol test to detect immunoglobulin G agglutinating antibody in bovine serum.

Agglutination Tests↗

PubMed1983

[Effect of 2-mercaptoethanol on the individual periods of the mitotic cycle].

Dynamics of the mitotic cycle of the KEPV cells being on different interphase stages at the start of a 20 hour 2-mercaptoethanol (0.001 M) treatment has been studied during the treatment and for 11 hours after washing out the agent. The KEPV cells affected by mercaptoethanol during the interphase (G1, S, G2) were shown to continue their passage through the cycle to enter mitosis, but part of the cells of the S period and of the first half of the G2 period were arrested in the interphase. In the presence of mercaptoethanol, mitotic cells reach the metaphase stage, and their further behaviour depends on the duration of the treatment. For the first 8 hours of treatment, a phase of "unstable block" exists for cells that were in S and G2 periods at the beginning of treatment, while other cells are transformed into K-metaphases. 8 hours later a phase of "stable block" occurs and all the normal metaphases are transformed into K-metaphases. After washing out the culture from mercaptoethanol the cells are ejected from the block in K-metaphase. The transformation from K-metaphase into the normal metaphase is realised in the course of this process. The cells which were in S and G2 periods at the beginning of the treatment are ejected from the block simultaneously after washing, while the cells of the G1 period--with a small delay. After washing out mercaptoethanol the cells that were in the interphase (G1, S, G2) at the beginning of the treatment are capable of producing both multipolar mitoses and mitoses without cytotomy.

Animals↗

PubMed1965

COMPLEMENT AND HEMOLYTIC ANTIBODY: CHANGES IN THEIR ACTIVITY INDUCED BY MERCAPTOETHANOL.

Cell-bound complement components are not destroyed by mercaptoethanol. Destruction of cell-bound hemolytic antibody was prevented by cell-bound complement components. In the absence of cells, the complement components C'3 and C'4 were most susceptible to destruction by mercaptoethanol; C'1, C'1a, and C'2 were most resistant. Mercaptoethanol (0.01M) increases C'1 activity, and this increase is not due to activation of C'1 to C'1a. Destruction of some components required both mercaptoethanol and iodoacetamide treatment.

Animals↗

PubMed1985

Reduced glutathione in Chinese hamster ovary cells protects against inactivation of 3-hydroxy-3-methylglutaryl coenzyme A reductase by 2-mercaptoethanol disulfide.

When the disulfide of 2-mercaptoethanol (ESSE) is added to the medium of cultured Chinese hamster ovary (CHO) cells, a time and concentration dependent release of 2-mercaptoethanol to the medium is observed. The reduction of ESSE to 2-mercaptoethanol by cells is a saturable process, the rate being approximately 50 nmoles of 2-mercaptoethanol per mg cell protein for an hour upon exposure to 250 microM ESSE. Reduction rate of ESSE by cells attached to a substratum is independent of glucose and insulin for periods up to 4 hours. However, in detached cells, swirled in suspension, addition of glucose and insulin is necessary in order to obtain a linear reduction rate of ESSE. The rate limiting enzyme in the sterol biosynthetic pathway, 3-hydroxy-3-methyl-glutaryl Coenzyme A reductase (E.C. 1.1.1.34), is inhibited by ESSE when isolated from CHO cells but total nonsaponifiable lipids synthesis from [2-14C]-acetate in intact cells is not affected by ESSE at concentrations up to 500 microM. Cytosolic reduced glutathione can spontaneously exchange disulfide bonds with ESSE and thus prevent it from inhibiting the reductase. Cultured cells respond to ESSE administration by elevating their total and acid-soluble glutathione levels. The use of ESSE as a perturbant of the GSH Status in cells is discussed.

Animals↗

PubMed2002

Reactivity of the NS2/3(907-1206)ASK(4) protein with beta-mercaptoethanol studied by electrospray ion trap mass spectrometry.

The present work reports a mass spectrometric investigation of the NS2/3 protein, a protease from hepatitis C virus (HCV). During routine protein manipulation, in the presence of 100 mM beta-mercaptoethanol and under denatured conditions, the protein was unexpectedly modified at its cysteine residues, and the increased molecular weight corresponded to one molecule of beta-mercaptoethanol bound. The modified protein, once refolded, was found to be less active than the unmodified one. The aim of this work was to investigate whether the reactivity of cysteines with beta-mercaptoethanol involves one specific, highly reactive residue of the sequence, or if the modification is a random process. Liquid chromatography (LC) coupled on-line with an electrospray ion trap mass spectrometer was used to identify the modification sites. It was found that five cysteines out of nine had reacted with beta-mercaptoethanol, none of them showing a significantly higher reactivity than the others. 95% of sequence coverage was obtained.

Amino Acid Sequence↗

PubMed1992

Mercaptoethanol and dithiothreitol decrease the difference of electrochemical proton potentials across the yeast plasma and vacuolar membranes and activate their H(+)-ATPases.

Mercaptoethanol and dithiothreitol (DTT) inhibited the acidification of external medium by Saccharomyces carlsbergensis cells and protoplasts during glucose oxidation. The inhibition was also observed when cells were incubated with mercaptoethanol or when mercaptoethanol and DTT were used to prepare protoplasts. Experiments with S. carlsbergensis plasma membrane vesicles and vacuoles showed these thiol reagents to inhibit ATP-dependent generation of delta pH and Em across plasma membrane vesicles and vacuoles but to activate their H(+)-ATPases. Mercaptoethanol and DTT are suggested to de-energize plasmalemma as well as tonoplast by increasing their H(+)-permeability and to disturb the cell ion homeostasis.

Cell Membrane↗

PubMed1994

Sequential methylation of 2-mercaptoethanol to the dimethyl sulfonium ion, 2-(dimethylthio)ethanol, in vivo and in vitro.

Thioether methyltransferase (S-adenosyl-L-methionine: thioether S-methyltransferase; EC 2.1.1.96) catalyzes the methylation of X in compounds of the type R-X-R'(X = S, Se, Te), yielding a methyl onium ion. Previous results using mice have demonstrated a role for thioether methyltransferase in the conversion and clearance of thioethers by methylation to more water-soluble methyl sulfonium ions suitable for excretion in the urine. A potential major physiological source of thiethers is reactions catalyzed by microsomal thiol methyltransferase (S-adenosyl-L-methionine: thiol S-methyltransferase; EC 2.1.1.9), which has been shown to methylate a diverse range of aliphatic sulfhydryl compounds. This study provides evidence for the sequential methylation of the aliphatic thiol, 2-mercaptoethanol, first to the methyl thioether, 2-(methylthio)ethanol, by thiol methyltransferase followed by methylation of this methyl thioeter to the dimethyl sulfonium ion, 2-(-dimethylthio)ethanol, by thioether methyltransferase. This sequence of reactions was demonstrated in vivo by injecting mice i.p. with radioactive 2-mercaptoethanol and analyzing the labeled methylated products, 2-(methylthio)ethanol and 2(dimethylthio)ethanol, in the urine by HPLC. In addition, the system converting 2-mercaptoethanol to 2-(dimethylthio)ethanol was reconstituted in vitro using solubilized mouse liver microsomes as a source of thiol methyltransferase and purified thioether methyltransferase from mouse lung. The results of these in vivo and in vitro studies established the sequential methylation of 2-mercaptoethanol by these two enzymes.

Animals↗

PubMed1978

Effects of 2-mercaptoethanol and aging in vitro on 17beta-hydroxysteroid oxidoreductase of guinea pig liver microsomes.

When microsomes were prepared in 2-mercaptoethanol Vmax for 17beta-hydroxysteroid oxidoreductase (17beta-HSD) was greater, the Km for NAD+ was greater and the Km for testosterone lower than in its absence. During storage at 4 degrees Vmax increased in the presence of 2-mercaptoethanol and decreased in its absence; Km values for testosterone and NAD+ increased during storage in both cases. The presence or absence of 2-mercaptoethanol did not affect the extent or time-course of inactivation of 17beta-HSD by trypsin or phospholipase A. Furthermore, no differences were detected in sedimentation properties on sucrose density gradients suggesting that the differences and changes in the kinetic behavior of 17beta-HSD reflect a conformational flexibility at the active site and are not due to extensive changes in the structure of the microsomes. 17beta-HSD exposed to 2-mercaptoethanol was subject to substrate inhibition by testosterone, a type of inhibition not previously reported for this enzyme.

17-Hydroxysteroid Dehydrogenases↗

PubMed1993

The inhibition of corrinoid-catalyzed oxidation of mercaptoethanol by methyl iodide: mechanistic implications.

The cobalamin coenzymes (5'-deoxyadenosyl- and methylcobalamin) and their cobinamide counterparts (5'-deoxyadenosyl- and methylcobinamide) catalyze the oxidation of 2-mercaptoethanol to its disulfide with hydrogen peroxide formation under aerobic conditions. The reactions are blocked by methyl iodide. Inhibition by methyl iodide is apparently due to the formation of the trans dialkyl corrinoids: methyl(adenosyl)cobalamin, dimethylcobalamin, methyl(adenosyl)cobinamide, and dimethylcobinamide, respectively. When the reaction system is illuminated with visible light, inhibition is released and a dramatic enhancement in the rate of oxygen consumption occurs. For reactions catalyzed by adenosyl- and methylcobalamin and then inhibited by methyl iodide, the rates observed during photolysis approach those obtained with aquacobalamin. For reactions catalyzed by adenosyl- and methylcobinamide and then inhibited by methyl iodide, the rates observed during photlysis approach those obtained with diaquacobinamide. Thus, both trans axial carbon-cobalt bonds in the putative dialkyl corrinoid are homolyzed during photolysis. In contrast to these results, the catalysis of the aerobic oxidation of 2-mercaptoethanol by aquacobalamin is only weakly inhibited by methyl iodide. This observation suggests that aquacob(II)alamin is produced during the catalysis of this reaction. Superoxide, the anticipated product of the reaction between aquacob(II)alamin and dioxygen, is formed during aquacobalamin-catalyzed 2-mercaptoethanol oxidation since superoxide dismutase decreases the rate of oxygen consumption by 50%. However, the enzyme has no effect on oxygen uptake during reactions catalyzed by cobalamin coenzymes and their cobinamide counterparts. These corrinoid catalysts apparently transfer two electrons to dioxygen from cobalt(I) intermediates formed during the reactions. Nitrogenous bases inhibit corrinoid-catalyzed thiol oxidation by competing with 2-mercaptoethanol for axial-ligand coordination sites on the catalyst. In contrast to the inhibition observed with methyl iodide, visible light has no effect on the inhibition obtained with nitrogenous bases.

Catalysis↗

PubMed1995

13C-NMR spectroscopic studies of 2-mercaptoethanol-stimulated glutathione synthesis in the intact ocular lens.

13C-NMR spectroscopy was employed non-invasively for the real-time measurement of the rates of glutathione synthesis in intact rabbit lenses supported in organ culture containing L-[3-13C]cysteine. Supplementation of the organ culture medium with 2-mercaptoethanol resulted in a dose- dependent enhancement of lenticular glutathione synthesis rates (dose for 50% maximal effect = 125 microM). At the most effective concentration (400 microM) 2-mercaptoethanol increased the rate of glutathione synthesis 163% relative to the rate observed under control conditions. The mechanism of action for this effect was investigated in intact lenses using antagonists of specific amino acid uptake systems. These experiments demonstrated that the enhanced rates of glutathione synthesis observed in the presence of 2-mercaptoethanol were due to the affinity of the mixed-disulfide formed between cysteine and 2-mercaptoethanol for L system amino acid uptake, thereby providing a mechanism for increasing intracellular cysteine levels by circumventing normal cellular cysteine uptake pathways in the lens. Because of the role of cysteine as the rate limiting substrate in lenticular glutathione biosynthesis, these results suggest a potential strategy to prevent tissue opacification associated with depleted glutathione levels.

Animals↗

PubMed1989

Application of rapid-scanning, stopped-flow spectroscopy to the characterization of intermediates formed in the reactions of L- and D-tryptophan and beta-mercaptoethanol with Escherichia coli tryptophan synthase.

The reactions of the alpha 2 beta 2 complex of Escherichia coli tryptophan synthase with D- and L-Trp and the presteady-state reaction of L-Ser and beta-mercaptoethanol under different premixing conditions have been investigated by rapid-scanning stopped-flow (RSSF) UV-visible spectroscopy. The reaction of alpha 2 beta 2 with L-Ser and beta-mercaptoethanol occurs in 3 detectable relaxations with rates similar to the 3 relaxations seen in the partial reaction with L-Ser and in the reaction with L-Ser and indole. The presteady-state phase of the reaction of beta-mercaptoethanol with the alpha-aminoacrylate intermediate is characterized by 2 relaxations. The RSSF spectra for this reaction show that the spectral changes that take place in these 2 phases are essentially identical. The L-Trp reaction is biphasic, and the spectral changes occurring in each phase of the reaction also are identical. The 2 new spectral bands formed (lambda max congruent to 420 nm and congruent to 476 nm) are assigned as the L-Trp external aldimine (Schiff's base) and L-Trp quinonoid intermediates, respectively. The reaction of D-Trp also is biphasic. Analysis of first and second derivatives of the RSSF spectral changes give evidence for the formation of spectral bands with lambda max of approximately 423 nm, approximately 450 nm, and approximately 478 nm. The positions and shapes of these bands suggest a D-Trp external aldimine structure (423 nm) and a quinonoidal species (450 and 478 nm). However, product studies do not support this latter assignment. The behavior of the D- and L-Trp reactions and the reaction of beta-mercaptoethanol with the alpha-aminoacrylate strongly indicate the pre-existence of 2 slowly equilibrating forms of the internal aldimine and of the alpha-aminoacrylate.

Escherichia coli↗

PubMed1978

Thiolysis of Nim-2,4-dinitrophenyl-histidine peptides with 2-mercaptoethanol. An explannation for the pH optimum.

The thiolysis of Nim-2,4-dinitrophenyl-histidine peptides with 2-mercaptoethanol demonstrates an optimal rate between pH 8.5 and 9.0. Base lability of both reactants and product was investigated as a possible cause for the pH optimum. N-2,4-Dinitrophenylimidazole, a model for Nim-2,4-dinitrophenylhistidine peptides, 2-mercaptoethanol and the product of thiolysis, 2,4-dinitrophenyl-S-mercaptoethan-2-ol, were subjected to aqueous basic conditions (pH 8.5 to 12.0). The reactions were followed spectrophotometrically, and products were identified by comparison of their ultra-violet spectra with commercially available or synthetic compounds. Mechanisms and rate constants for base hydrolysis of 2,4-dinitrophenyl-thio ethers are presented. Although N-2,4-dinitrophenylimidazole and 2,4-dinitrophenyl-S-mercaptoethan-2-oldohydrolyze, it is the oxidation of 2-mercaptoethanol to 2-mercaptoethanol disulfide which results in the decreasing rate of thiolysis above pH 9.0.

Dinitrobenzenes↗

PubMed1980

Jack bean urease (EC 3.5.1.5). III. The involvement of active-site nickel ion in inhibition by beta-mercaptoethanol, phosphoramidate, and fluoride.

Interaction of beta-mercaptoethanol with urease produces large, rapid and fully reversible spectral changes in that part of the electronic absorption spectrum which is associated with the tightly bound nickel ions. The spectrophotometrically determined value of the dissociation constant of the beta-mercaptoethanol-urease complex (0.9 +/- 0.05 mM at pH 7.12 and 25 degrees C) is in agreement with the Ki (0.72 +/- 0.26 mM) for beta-mercaptoethanol acting as a competitive inhibitor in the hydrolysis of urea. This constitutes direct evidence that the nickel in jack bean urease is at the active site. Inhibition of urease by phosphoramidate is slowly achieved and slowly reversed, and upon reactivation of the isolated phosphoramidate-urease complex, phosphoramidate is regenerated in good yield. Spectrophotometric experiments indicate that phosphoramidate binds to nickel ion in urease. Competition with beta-mercaptoethanol was used to determine a dissociation constant (1.23 +/- 0.10 mM at pH 7.12 and 25 degrees C) for a fluoride-evidence is presented which indicates that in the presence of urea, a ternary complex (fluoride-urea-urease) is formed.

Amides↗

PubMedDate not supplied

[Toxicity of mercaptoethanol to mutant strains of the yeast Pichia methanolica growing on different carbon sources].

Addition of beta-mercaptoethanol at a concentration of 2-3 mM to media containing methanol, glucose, or yeast extract caused a 50% inhibition of the growth of wild-type yeast Pichia methanolica; mercaptoethanol at a concentration of 0.7 to 25 mM inhibited the growth of the mutant strain ecr1. The mutation mth1 of P. methanolica repressed its ability to consume methanol and was accompanied by the loss of alcohol oxidase (EC 1.1.3.13) activity. beta-Mercaptoethanol restored the ability of mth1 mutant cells to grow on methanol and stimulated their growth under derepression conditions. The growth effect of beta-mercaptoethanol during derepression was accompanied by partial restoration of alcohol oxidase activity.

Carbon↗

PubMed1992

[Use of 2-mercaptoethanol in cell culture].

Survival and growth in in vitro cultivation of lymphocytes, lymphoma cells and some other cells including human carcinomas are profoundly improved by 2-mercaptoethanol. These cells hardly take up cystine, an essential nutrient in the culture medium, but in the presence of 2-mercaptoethanol they can utilize cystine. Recently it has been found that 2-mercaptoethanol is effective in the in vitro cultivation of pathogenic trypanosomes and in the in vitro development of bovine embryos. The mechanisms by which 2-mercaptoethanol improves the survival and growth of these cells are described.

Animals↗

PubMed1981

[Dynamics of the mitotic cycle and mitosis anomalies in 2-mercaptoethanol action on pig embryo kidney tissue culture cells].

The effect of 2-mercaptoethanol on the dynamics of mitotic cycle was examined in cells of a porcine embryo kidney culture. 2-mercaptoethanol is shown to block cell division in C-metaphase-like figures. After the agent removal the block was stopped, and cells proceeded to a normal metaphase again. The presence of 2-mercaptoethanol does not prevent the S/G2 transition, the entry of cells to the prophase and then to the normal metaphase. At the same time, the length of G2-period of interphase appears to remain normal. In a porcine embryo kidney culture 2-mercaptoethanol induced multipolar mitoses and mitoses without cytokinesis. The number of multipolar mitoses increased with the increase in the time of incubation.

Animals↗

PubMed1965

The enzymic reduction of nicotinamide-adenine dinucleotide by 2-mercaptoethanol.

1. The reduction of NAD(+), by an enzyme preparation from rat liver, in the presence of 2-mercaptoethanol is reported. 2. It is suggested that the NAD(+)-linked alcohol dehydrogenase in the extract transfers hydrogen from 2-mercaptoethanol to NAD(+). 3. Both yeast and horse-liver alcohol dehydrogenases were observed to reduce NAD(+) in the presence of 2-mercaptoethanol. 4. Some interactions of 2-mercaptoethanol, cysteine or hydroxylamine with the alcohol dehydrogenases from rat liver, horse liver and yeast are discussed.

Journal Article↗