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PubMed1980

[Reversible oxidation-reduction of NAD by hydrogen, catalyzed by soluble hydrogenase from Alcaligenes eutrophus Z-1].

The kinetics of NAD reduction by hydrogen, catalyzed by soluble hydrogenase from the hydrogen bacterium A. eutrophus Z-1 within a wide range of NAD substrate concentrations and pH were studied under aerobic and anaerobic conditions. The autocatalytic type of the reaction (with an induction period) and positive kinetic cooperativity with respect to NAD substrate at pH values greater than 8.0 were observed. A steady hydrogen release in a two-enzyme system involving hydrogenase, formiate dehydrogenase, formiate and NAD was demonstrated. A multistep pattern of the reaction mechanism of NAD reduction allowing to explain the autocatalytic type of NAD reduction by hydrogen as well as insensitivity of the reaction to air oxygen were proposed. Possible types of regulation of the soluble hydrogenase activity in the cell are discussed.

Aerobiosis↗
PubMedDate not supplied

[Growth and proton-potassium exchange in Enterococcus hirae: protonophore effect and the role of oxidation-reduction potential].

Enterococcus hirae ATCC 9790 are able to grow under anaerobic conditions during the fermentation of sugars (pH 8.0) in the presence of the protonophore carbonylcyanide-m-chlorophenylhydrazone at a lesser specific growth rate. As bacteria grow, the acidification of the external medium and a drop in the redox potential from positive to negative (up to -220 mV) values occur. The reducer dithiothreitol, which maintains the negative values of the redox potential, increases the growth rate and acidification of the medium, recovering thereby the effect of the protonophore (without interacting with it). Conversely, the impermeable oxidizer ferricyanide, while maintaining positive values of the redox potential, inhibits the bacterial growth. These results indicate the role of the proton-motive force and importance of reducing processes in bacterial growth. The proton-potassium exchange is inhibited by carbonylcyanide-m-chlorophenylhydazone but is restored with dithiothreitol. Dithiothreiol is able to substitute the proton-motive force; however, ferricyanide and dithiothreitol may also directly affect the bacterial membrane.

Anaerobiosis↗
PubMedDate not supplied

[Action of a vitamin complex with oxidative-reductive properties on the course of acute myocardial hypoxia and ischemia].

Experiments on mice with simulated isobaric hypoxia and anoxia have demonstrated marked antihypoxic action of a complex of vitamins with electron-acceptor activity (ascorbic acid, riboflavine mononucleotide, lipoic acid, nicotinamide). In dog experiments, the complex of vitamins reduced metabolic acidosis in the ischemia zone as shown by the lactate release test and increased the collateral coronary circulation. The protective action of the drug recorded in hypoxia and regional myocardial ischemia is regarded as linked with the ability of the vitamin complex to raise the conjugation of oxidation and phosphorylation in the mitochondria of a pathologically altered myocardium, as well as with its membrane-stabilizing action and inhibition of lipid peroxidation.

Acute Disease↗
PubMedDate not supplied

[Oxidation reduction processes in skin with psoriasis].

In the skin affected with psoriasis a pronounced increase in the redox processes intensity is observed, which influences the activity in the respiratory chain certain enzymes. These disturbances are stable as no complete normalization is observed in the activity in the studied enzymes after the clinical recovery.

Humans↗
PubMed1985

Effect of dinitrophenyl modification on oxidation-reduction of glutathione reductase from yeast.

Covalent modification of glutathione reductase (GR) from yeast with 1-fluoro-2,4-dinitrobenzene (FDNB) inhibited the NADPH-GSSG reductase activity completely. This modification also decreased the NADPH-thio-NADP+ transhydrogenase activity, stimulated the NADPH-oxidase activity, and induced the NADPH-cytochrome c reductase activity. Spectrophotometric titration showed that one tyrosine residue per FAD was modified with a dinitrophenyl group. The modified enzyme showed conversion of the two-electron reduced form (EH2) to the four-electron reduced form (EH4) in anaerobic conditions and conversion of EH2 to the oxidized form (E) in aerobic conditions. These results indicate that the modification of one tyrosine residue of the active site induces the instability of EH2.

Binding Sites↗
PubMed2005

Effectors of fatty acid oxidation reduction: promising new anti-ischaemic agents.

The heart is a pump, but also a furnace able to produce at each moment a large amount of energy and to adapt fast enough to face the changes in both fuel supply and energy demand. The pharmacological treatment of angina has been largely focused on the "pump" through hemodynamic agents aimed at decreasing cardiac effort to decrease energy demand. A new concept arose focusing the "furnace" through metabolic agents aimed at decreasing the oxygen cost of ATP production. This goal can be achieved by shifting energy production from fatty acid beta-oxidation to glucose oxidation. CPT1 inhibitors were developed to prevent the fatty acid entry into mitochondria but induced cardiac hypertrophy. Regulation of carnitine biology either by carnitine supply or by gamma-butyrobetaine hydroxylase inhibitors have led to controversial data both in pharmacological and clinical concerns. Trimetazidine and ranolazine increase the glucose/fatty acid oxidation balance and exhibit beneficial effects in animal studies as well as in clinical trials, both in monotherapy and in association with a traditional hemodynamic drug. The association of metabolic and hemodynamic agents brings additive benefits in angina, whereas associations of hemodynamics do not. The mechanism of these drugs has not been fully understood in terms of specific target. In animal studies, dietary docosahexaenoic acid allowed similar protection, through a mechanism related to membrane conformation without specific enzymic target. From the mechanistic research published in this field, enough has now been understood to foresee some future possible targets, mainly related to the cardiomyocyte fatty acid metabolism.

Acyl Coenzyme A↗
PubMed1988

The oxidation-state-dependent ATP-binding site of cytochrome c. Implication of an essential arginine residue and the effect of occupancy on the oxidation-reduction potential.

Arg-91 is not part of the active site of cytochrome c that mediates binding and electron transfer, yet it is absolutely conserved in eukaryotic cytochromes c, indicating a special function. The physicochemical properties of analogues are unaffected by the modification of this residue, so they can be used with confidence to study the role of Arg-91. We have established limiting conditions under which this residue alone is specifically modified by cyclohexane-1,2-dione, and have subsequently shown that ATP, and to a lesser extent ADP or Pi, protects it from the action of the reagent in an oxidation-state-dependent manner. These observations strongly support the idea that this site exerts a controlling influence on cytochrome c activity in the electron transport or other cellular redox systems, and we have commenced a study of how that influence might operate. We find that the redox potentials of both cytochrome c and analogue are little affected by changing ATP or Pi concentrations.

Adenosine Triphosphate↗
PubMed1994

Modulation of the oxidation-reduction potential of the flavin in lipoamide dehydrogenase from Escherichia coli by alteration of a nearby charged residue, K53R.

The epsilon-amino group of a lysine residue occupies a position within bonding distance of the flavin N5 and the bound NADPH pyridinium C4' in glutathione reductase, and it has been suggested that this positive charge influences the redox potential of the FAD [Pai & Schulz (1983) J. Biol. Chem. 258, 1752]. A conserved lysine residue occupies a similar position in lipoamide dehydrogenase. This residue has been replaced by an arginine in lipoamide dehydrogenase from Escherichia coli to give K53R. The spectral and redox properties of the FAD in K53R as well as the interaction of the flavin with bound NAD+ are profoundly affected by the change. K53R does not catalyze either the dihydrolipoamide-NAD+ or the NADH-lipoamide reactions except at very low concentrations of the reducing substrate. The absorbance spectrum of K53R in the visible and near-ultraviolet is little changed from that of wild-type enzyme, but in contrast, the spectrum of K53R is sensitive to pH with an apparent pKa = 7.0. Unlike the wild-type enzyme, the binding of beta-NAD+ to K53R alters the spectrum and indicates an apparent Kd = 7.0 microM at pH 7.6. The flavin fluorescence is partially quenched, and the visible and near-ultraviolet circular dichroism spectrum is changed by beta-NAD+. K53R is extensively reduced (mostly EH4) by 2 equiv of dihydrolipoamide/FAD while the wild-type enzyme is only partially reduced (mostly EH2). The rate of this reduction is lowered by approximately 3-fold relative to the wild-type enzyme.(ABSTRACT TRUNCATED AT 250 WORDS)

Circular Dichroism↗
PubMed1991

Modulation of transcription factor NF-kappa B binding activity by oxidation-reduction in vitro.

NF-kappa B is a widely used regulator of inducible and tissue-specific gene control. In the cytosol, when complexed to an inhibitory molecule, I kappa B, NF-kappa B is in an inactive form and cannot bind DNA. Activation of cells with appropriate stimuli results in the dissociation of NF-kappa B from I kappa B and its translocation to the nucleus as an active binding protein. We now demonstrate that NF-kappa B binding in vitro can be inhibited by agents that modify free sulfhydryls. Binding is eliminated after treatment with N-ethylmaleimide, an alkylating agent, and diamide, an oxidizing agent. The diamide effect can be reversed by 2-mercaptoethanol. Further, 2-mercaptoethanol acts synergistically with deoxycholate plus Nonidet P-40 in converting inactive cytosolic NF-kappa B to an active DNA-binding form. It is therefore possible that modulation of the redox state of NF-kappa B could represent a post-translational control mechanism for this factor.

Cell Nucleus↗
PubMed1986

[Effect of kainic acid on the metabolism of intracellular calcium and oxidation-reduction processes in structures of the cerebral cortex].

The dynamics of calcium ions bound within intracellular membranes (Ca2+b), changes of redox--state and bioelectrical activity were studies in vital brain preparation after kainic acid (KA) application either to the micro--zones iontophoretically or to the whole surface of the preparation. The Ca2+b dynamics depended on KA dose and included release of Ca2+b as well as bounding of calcium attracted from extracellular space. The early period of the reaction consisted of an increased intracellular reduction equivalents and a release of Ca2+b. Theme correlating processes were followed by "seizure" activity specific for the KA effect. The calcium free bounding effect started to prevail with increasing KA dose.

Animals↗
PubMed2006

Entamoeba histolytica: an ecto-phosphatase activity regulated by oxidation-reduction reactions.

In this work, an ecto-phosphatase activity of Entamoeba histolytica was characterized using intact cells. This activity presented the following biochemical characteristics: (i) it hydrolyzes p-NPP with V(max) of 8.00+/-0.22 nmol p-NP x h(-1) x 10(-5) cells and K(m) of 2.68+/-0.25 mM; (ii) it is inhibited by acid phosphatase inhibitors, such as sodium molybdate (K(i)=1.70+/-0.24 microM) and sodium fluoride (K(i)=0.25+/-0.02 mM); (iii) it also showed high sensitivity to phosphotyrosine phosphatase inhibitors, such as sodium orthovanadate (K(i)=1.07+/-0.14 microM), bpV-PHEN (K(i)=0.38+/-0.02 microM) and mpV-PIC (K(i)=0.39+/-0.04 microM). Zn(2+), an oxidizing agent, decreased the enzymatic activity in 50%. DTT and GSH, two reducing agents, enhanced the activity twofold. The non-invasive E. histolytica and free-living E. moshkovskii were less efficient in hydrolyzing p-NPP than the pathogenic E. histolytica suggesting that this enzyme could represent a virulence marker for this cell.

Animals↗
PubMed1980

Oxidation-reduction properties and complexation reactions of the iron-molybdenum cofactor of nitrogenase.

The interactions of the iron-molybdenum cofactor, FeMoco, isolated from acid-treated Azotobacter vinelandii molybdenum-iron protein (Av1) with EDTA and thiophenol in N-methylformamide solution have been reinvestigated. Our studies show that EDTA alone is sufficient to eliminate the EPR signal of dithionite-reduced FeMoco. Neither light/5-deazaflavin nor carbon monoxide are required, which implies that this EPR-silent form of FeMoco does not correspond to the EPR-silent, substrate-reducing state of Av1. As EDTA-treated FeMoco does not regain EPR activity on addition of sodium dithionite or thiophenol, it is apparently distinct from the EPR-silent form of either dye-oxidized FeMoco or dye-oxidized Av1. Thiophenol sharpens the EPR signal of dithionite-reduced FeMoco and shifts the g = 3.3 feature to g = 3.6. This shift is complete at 1:1 ratio of thiophenol/Mo atom, while the EDTA effect requires about 40 molecules/Mo atom. Thiophenol and EDTA probably affect different sites of FeMoco. The binding of either reactant does not affect the activity of FeMoco as measured by its ability to reconstitute extracts of A. vinelandii mutant UW45.

Azotobacter↗
PubMed1976

[The change of hyaluronic acid of the vitreous humour by oxidation-reduction-systems (author's transl)].

Purified hyaluronic acid of ox vitreous humour was isolated treating the acetone precipitate of a vitreous humour homogenate with 1 M NaCl solution and thereafter with cetylpyridiniumchloride. Both disc-electrophoresis and hydroxyproline content proved the absence of collagen in the purified hyaluronic acid. FeSO4, ascorbate, and cysteine changed the hyaluronic acid molecule and lowered the viscosity of the hyaluronic acid solution, EDTA alone did not affect the viscosity but enhanced the effectiveness of iron ions or ascorbate on the viscosity of the solution. Catalase prevented the reduction of the viscosity by the above mentioned substances. Therefore, it is suggested that H2O2 and free radicals are generated during the reaction. The free radicals produced are responsible for the change of the hyaluronic acid molecule.

Animals↗
PubMedDate not supplied

[EPR study of electron transport in higher plant photosynthetic systems. II. Effect of temperature on the kinetics of photoinduced oxidation-reduction transformations of P700].

A sharp fall of ESR signal I is observed at temperature decrease while switching on light of 600 nm on the background of light of 707 nm; kinetics of the initiation of the signal under the illumination of light of 707 nm gets more complicated; the induction phase induced by previous illumination with the light of 600 nm increases.

Darkness↗
PubMed1976

[Nitrotyrosyl]cytochrome c. Studies of the effect of iron binding, protein denaturants and oxidation-reduction potentials.

Static measurements of the reaction of ligand binding were done by conventional spectrophotometry. The ligand-binding reactions with nitrated cytochrome c were performed with imidazole, iminazole, CO and NO. The stoicheiometry was found to be 1:1, and the stability constants for the complexes formed between the nitrated cytochrome c and the ligands are: 2.58 X 10(4) M-1 (imidazole); 1.01 X 10(2) M-1 (iminazole); 3.6 X 10(4) M-1 (CO); 2.74 X 10(4) M-1 (NO). It was found that the electrometric potentials at pH 7.0 and 25degreesC of [aminotyrosyl]cytochrome c are E'o form II = 0.115 V and E'o form I = 0.260 V, where forms I and II are two species of protein co-existing in the protein solution. The isoelectric point for the oxidized form of [nitrotyrosyl]cytochrome c was 10.05, at 4degreesC.

Carbon Monoxide↗