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PubMed1993

Effect of storage temperature on the activity of superoxide dismutase, catalase, glutathione peroxidase, glutathione reductase and glutathione S-transferase in rat liver and kidney homogenates.

The behavior of the catalytic activities of the enzymes superoxide dismutase, catalase, glutathione peroxidase, glutathione S-transferase and glutathione reductase was tested in rat liver and kidney homogenates stored at 4, -20 and -70 degrees C and in corresponding tissue samples stored at -70 degrees C. The stabilities of enzymes were different for various enzymes and were dependent on the organ (liver, kidney) and the storage temperature. The storage temperature of -70 degrees C guaranteed the best stability and the five enzymes investigated were sufficiently stable in preserved tissue samples or in homogenates prepared with conventional mannit/sucrose homogenization solution. Under such conditions, these enzymes were stable over at least 4 or 1 weeks, respectively.

Animals↗
PubMed1996

Photoinactivation of trypanothione reductase and glutathione reductase by Al-phthalocyanine tetrasulfonate and hematoporphyrin.

The irradiation of Trypanosoma congolense trypanothione reductase (TR), human erythrocyte (HGR) and yeast glutathione reductase (YGR) with visible light in the presence of Al-phthalocyanine tetrasulfonate (A1PcS4) or hematoporphyrine (Hp) caused a time-dependent inactivation of these enzymes. TR was inactivated more rapidly than either HGR or YGR. Half-maximal rates of inactivation were determined in the presence of 100 microM Hp and 1.4-17 microM AlPcS4. The photosensitized irradiation modified the disulfide substrate-binding sites of these enzymes, most likely the conserved catalytic histidine residue. In the dark, AlPcS4 acted as a reversible inhibitor competitive with the disulfide substrate of TR and HGR. These findings suggest the possible use of photosensitized irradiation for preventing the transmission of trypanosomiasis by blood transfusion.

Animals↗
PubMed2002

Drug-resistant human lung cancer cells are more sensitive to selenium cytotoxicity. Effects on thioredoxin reductase and glutathione reductase.

The human U-1285 and GLC(4) cell lines, both derived from small cell carcinoma of the lung, are present in doxorubicin-sensitive (U-1285 and GLC(4)) and doxorubicin-resistant MRP-expressing (U-1285dox and GLC(4)/ADR) variants. These sublines were examined here with respect to their susceptibilities to the toxic effects of selenite and compared to the toxic effects of selenite on the promyelocytic leukemia cell line HL-60 and its doxorubicin-resistant P-glycoprotein expressing variant. The drug-resistant U-1285dox and GLC(4)/ADR sublines proved to be 3- and 4-fold, respectively, more sensitive to the cytotoxicity of selenite than the drug-sensitive U-1285 and GLC(4) sublines, whereas no difference was observed between the HL-60 sublines. The presence of doxorubicin at a concentration equal to the IC(10) did not significantly potentiate the toxic effects of selenite. The presence of selenite did not significantly affect the expression of the multi-drug resistant proteins (MRP1, LRP and topoisomerase IIalpha) in the drug-resistant cells. The activities of thioredoxin reductase (TrxR) were higher (50 and 25%, respectively) in the drug resistant cell sublines U-1285dox and GLC(4)/ADR compared to the drug-sensitive parental lines. The activity of glutathione reductase (GR) was essentially the same in the drug-sensitive and -resistant cell lines. Exposure to selenite resulted in a 4-fold increase in both TrxR and GR activities in U-1285 cells, an effect, which was less pronounced in the presence of doxorubicin. Under similar conditions the increase in the TrxR activity in the resistant U-1285dox cell line, was only 30% and the activity of GR was unaltered. Different responses in the activity of the key enzymes in selenium metabolism are one possible mechanism explaining the differential cytotoxicity of selenium in these cells.

Blotting, Western↗
PubMed1989

A comparison of glutathione reductase and glutathione peroxidase activities in patients with rheumatoid arthritis and healthy adults.

A 30% increase in erythrocyte glutathione peroxidase (GP) activity was found in patients with rheumatoid arthritis when compared with healthy controls (p = 0.001) whereas the increase in glutathione reductase (GR) was statistically insignificant. No correlation was found between the activities of the enzymes and the erythrocyte sedimentation rate (ESR). The enzyme activities were independent of age, sex, or type of drug treatment of the patients. A possible interpretation of the results is presented.

Adult↗
PubMed1994

Mechanism of inhibition of trypanothione reductase and glutathione reductase by trivalent organic arsenicals.

The dithiol trypanothione, novel to trypanosomatids and analogous to glutathione in mammalian systems, has been shown to interact with anti-trypanocidal trivalent arsenical drugs forming a stable adduct, MelT. This adduct is a competitive inhibitor of the flavoprotein trypanothione reductase, responsible for maintaining intracellular trypanothione in the reduced form. Since trypanothione reductase and the analogous glutathione reductase both contain catalytically active sulphydryl groups we have examined the ability of several arsenicals to differentially inhibit these enzymes. Melarsen oxide [p-(4,6-diamino-s-triazin-2-yl)aminophenylarsenoxide] potently inhibits both enzymes in two stages, the first being essentially complete within 1 min, the second being time dependent, exhibiting saturable pseudo-first-order kinetics with kinact of 14.3 x 10(-4) s-1 and 1.06 x 10(-4) s-1 and Ki of 17.2 microM and 9.6 microM for trypanothione reductase and glutathione reductase, respectively. Inhibition requires prior reduction of the enzyme by NADPH and can be reversed by excess dithiols or prevented by MelT in the case of trypanothione reductase. In both cases a time-dependent loss of the characteristic charge-transfer absorbance band at 530 nm is observed upon addition of arsenical to pre-reduced enzyme, which with excess NADPH leads to a spectrum resembling the EH4 form and is accompanied by an increased ability to reduce molecular oxygen. A model for inhibition is proposed where, first, free arsenical and previously reduced enzyme immediately establish an equilibrium with an inactive monothioarsane enzyme-inhibitor complex involving the interchange cysteine distal to the FAD; second, a subsequent rearrangement about the sulphur-arsenic bond leads to the binding of the arsenical to the charge-transfer cysteine, proximal to the FAD, forming a more stable dithioarsane complex. Molecular modelling suggests that the differences in kinetic behaviour of the two enzymes can be attributed to structural features of their respective disulphide-binding sites. Incubation of reduced trypanothione reductase with excess dihydrotrypanothione and melarsen oxide prevents direct inhibition of the enzyme, suggesting that dihydrotrypanothione acts as a protectant in vivo, preventing the direct modification of trypanothione reductase by sequestering the arsenical as MelT.

Animals↗
PubMed1995

Age-dependent effects of t-BuOOH on glutathione disulfide reductase, glutathione peroxidase, and malondialdehyde in the brain.

Intracerebroventricular t-butyl hydroperoxide has been reported to induce damage to many types of brain cells. t-Butyl hydroperoxide administration increases glutathione disulfide levels and decreases levels of glutathione. Young adult mice may be more protected from t-butyl hydroperoxide than mature mice due to their higher glutathione levels, even after the administration of t-butyl hydroperoxide. This leads to our current study, investigating glutathione peroxidase and glutathione disulfide reductase in 2-mo-old and 8-mo-old mice. Furthermore, malondialdehyde levels were measured with the thiobarbituric acid assay and compared between the two age groups. Mature mice detoxify glutathione disulfide less readily than young adult mice. Glutathione disulfide reductase activity increases in young adult mice after t-butyl hydroperoxide administration, but not in mature mice. Glutathione peroxidase activity is significantly lower in 8-mo-old than 2-mo-old mouse striatum after t-butyl hydroperoxide administration. Furthermore, malondialdehyde levels in the 8-mo-old striatum increase significantly 20 min after t-butyl hydroperoxide administration. This suggests that age plays a factor in protective mechanisms that are involved in oxidative stress in the brain.

Aging↗
PubMed1989

[The relation of glutathione reductase and diaphorase activity of glutathione reductase from Saccharomyces cerevisiae].

Glutathione reductase from S. cerevisiae (EC 1.6.4.2) catalyzes the NADPH oxidation by glutathione in accordance with a "ping-pong" scheme. The catalytic constant kcat) is 240 s-1 (pH 7.0, 25 degrees C); kcat for the diaphorase reaction is 4-5 s-1. The enzyme activity does not change markedly at pH 5.5-8.0. At pH less than or equal to 7.0, NADP+ acts as a competitive inhibitor towards NADPH and as a noncompetitive inhibitor towards glutathione. NADP+ increases the diaphorase activity of the enzyme. The maximal activity is observed, when the NADP+/NADPH ratio exceeds 100. At pH 8.0, NADP+ acts as a mixed type inhibitor during the reduction of glutathione. High concentrations of NADP+ also inhibit the diaphorase activity due to the reoxidation of the reduced enzyme by NADP+ at pH 8.0. The redox potential of glutathione reductase calculated from the inhibition data is--306 mV (pH 8.0). Glutathione reductase reduces quinoidal compounds in an one-electron way. The hyperbolic dependence of the logarithm of the oxidation constant on the one electron reduction potential of quinone is observed. It is assumed that quinones oxidize the equilibtium fraction of the two-electron reduced enzyme containing reduced FAD.

Dihydrolipoamide Dehydrogenase↗
PubMed1999

Evidence for the co-existence of glutathione reductase and trypanothione reductase in the non-trypanosomatid Euglenozoa: Euglena gracilis Z.

Two NADPH-dependent disulfide reductases, glutathione reductase and trypanothione reductase, were shown to be present in Euglena gracilis, purified to homogeneity and characterized. The glutathione reductase (Mr 50 kDa) displays a high specificity towards glutathione disulfide with a KM of 54 microM. The amino acid sequences of two peptides derived from the trypanothione reductase (Mr 54 kDa) show a high level of identity (81% and 64%) with sequences of trypanothione reductases from trypanosomatids. The trypanothione reductase is able to efficiently reduce trypanothione disulfide (KM 30.5 microM) and glutathionylspermidine disulfide (KM 90.6 microM) but not glutathione disulfide, nor Escherichia coli thioredoxin disulfide, nor 5,5'-dithiobis(2-nitrobenzoate) (DTNB). These results demonstrate for the first time (i) the existence of trypanothione reductase in a non-trypanosomatid organism and (ii) the coexistence of trypanothione reductase and glutathione reductase in E. gracilis.

Amino Acid Sequence↗
PubMed1990

Glutathione peroxidase, glutathione reductase and glutathione transferase activities in the human artery, vein and heart.

The continuous exposure to blood components, including prooxidants, makes the blood vessel wall susceptible to oxidative stress and free radical mediated reactions (Henning and Chow, 1988; Stamm et al., 1989; Halliwell and Gutteridge, 1984). Free radicals can be produced extracellularly via the respiratory bursts of activated neutrophils, or intracellularly, via oxidation of hypoxanthine by xanthine oxidase (Henning and Chow, 1988; Stamm et al., 1989; Rubanyi, 1988). Microsomal enzymes such as lipoxygenase and cyclooxygenase may also be a source of reactive species of oxygen (Henning and Chow, 1988; Stamm et al., 1989; Rubanyi, 1988; Mason et al., 1980). It has been proposed that free radicals are involved in the initiation and progression of various cardiovascular diseases including arteriosclerosis (Henning and Chow, 1988; Stamm et al., 1989; Yagi, 1988; Jürgens et al., 1987). Thus the adequacy of the defence systems against free radicals is critical for the susceptibility of blood vessel wall to oxidative damage. Among the enzymatic systems capable of protecting the cell against oxidative injury, selenium dependent glutathione peroxidase (Se-GSH-px), glutatione reductase (GSSG-rx) and glutathione transferase (GST) play a crucial role (Flohe' et al., 1976; Mannervik and Danielson, 1988). Using glutathione (GSH) as a cofactor, Se-GSH-px reduces H2O2 to water and organic hydroperoxides to the corresponding alcohols (Flohe' et al., 1976). This reaction leads to conversion of GSH into its oxidized form (GSSG). In the presence of NADPH, GSSG-rx is able to reduce the oxidized glutathione.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1978

[Interference by glutathione reductase in the "CK-MB-inhibition-test": elimination of the catalytic activity of glutathione reductase by anti-glutathione reductase (author's transl)].

Glutathione reductase interferes in the determiniation of creatine kinase-MB by the "CK-MB-inhibition-test". In 36 out of 55 serum samples with normal and elevated catalytic activities of creatine kinase, "negative" values greater than 14 U/l were obtained for the creatine kinase-MB. This interference by glutathione reductase is avoided by preincubation of the serum samples for 5 min with anti-glutathione reductase.

Catalysis↗
PubMed1986

Glutathione peroxidase, glutathione reductase and glutathione-S-transferase activities in the rhesus monkey lens as a function of age.

The activities of glutathione peroxidase, glutathione reductase and glutathione-S-transferase were determined in lenses from rhesus monkeys (Macaca mulatta) as a function of age. The ages ranged from 137 day old embryos to a 34 year old. Glutathione peroxidase activity (units/g lens) occurred at a very low level in lenses of fetuses and neonates, but increased dramatically with age, peaking in the adult of about 12 to 20 years of age and declining thereafter. Glutathione reductase activity (units/g lens) decreased throughout juvenile life, leveling off when adulthood was reached (at least 6 years of age). Glutathione-S-transferase activity showed considerable age-related variation. Calculations show that glutathione reductase is rate-limiting in the glutathione redox pathway.

Age Factors↗
PubMed1984

Changes of reduced glutathion, glutathion reductase, and glutathione peroxidase after radiation in guinea pigs.

In this series of experiments the protective action of reduced glutathion due to ionizing radiation has been studied. In the experimental group 18 guinea pigs were exposed to successive radiations of 150 rad 3 or 4 days apart. Total dose given amounted to 750 rad which is the LD50 for guinea pigs. Blood samples were taken 30 min after each exposure. The control series were sham radiated but otherwise treated identically. The cells of the removed blood samples were separated by centrifugation and were subjected to the reduced glutathion stability test. GSSGR, GPer, and LDH enzyme activities were also measured of which the latter served as a marked enzyme. It was found that LDH did not show any alteration after radiation. The reduced glutathion stability test showed a consistent but minor reduction (P greater than 0.05), in the experimental group. GSSGR enzyme activity on the other hand was reduced significantly (from 176.48 +/- 11.32 to 41.34 +/- 1.17 IU/ml of packed erythrocytes, P less than 0.001) in the same group. GPer activity showed a consistent but minor elevation during the early phase of the experimental group. It was later increased significantly beginning after 600 rad total radiation on the fourth session (P less than 0.050).

Animals↗
PubMedDate not supplied

[Activity of glutathione reductase and glutathione-S-transferase in rabbit brain tissue in the long-term post-traumatic period].

The glutathione-reductase and glutathione-S-transferase activities in the cortex and brain stem tissues of rabbits with post-traumatic epileptic reality (1 year after the light brain injury) was defined. An increase of glutathione-reductase activity in the cortex microsomal and stem mitochondrial fractions, and increase of glutathione-S-transferase activity in cortex and stem mitochondrial fractions was obtained. The conclusion is made that the activation of the anti-oxidant glutathione fermentative system is a long-term metabolic CNS adaptation in the case while mitochondrial oxidation and oxidative phosphorilation are disturbed.

Adaptation, Physiological↗
PubMed1975

[Optimized determination and properties of NADPH-dependent glutathione reductase in serum. Studies on serum glutathione reductase, I. (author's transl)].

Reaction conditions were optimized for the determination of serum glutathione reductase, which has not yet been investigated systematically. Imidazole was found to be the most suitable buffer material; the highest glutathione reductase activity in serum was always obtained with imidazole/HCl buffer, which, in contrast to all other tested buffers, also resulted in the maximal enzyme activity without preincubation. In imidazole buffer, the pH-activity curve of serum glutathione reductase shows a broad optimum between pH 6.5 and 6.9. A GSSG concentration of 2 mmol/l and a NADPH concentration of 0.43 mmol/l gave maximal enzyme activity and a linear reaction over 10 min up to 20 U/l test solution. An investigation of serum glutathione reductase activity from 100 clinically healthy probands gave values between 20 and 50 U/l. In the optimized assay system the glutathione reductase in the serum reacts specifically with GSSG and NADPH.

Autoanalysis↗
PubMed1990

Variations in the activity of glutathione reductase and the cellular glutathione content in relation to sensitivity to methylviologen in Escherichia coli.

To study the function of glutathione reductase and glutathione in Escherichia coli the coding sequence of the bacterial glutathione reductase gene (gor gene) was cloned into the vector pBR322, and the gor gene was expressed under the control of the promoter of the tetracycline-resistance gene (tet gene) in different Escherichia coli strains. Cells of the gor-mutant strain SG5 containing the vector pBR322 (SG5:pBR322) had no detectable glutathione reductase activity and a significantly lower total glutathione (GSH + GSSG) content relative to control cells of the strain JM101 (JM101: pBR322). The gor mutant cells were less sensitive to inhibition by methylviologen (as defined by changes in growth) than cells of the strain JM101. Elevated levels of both glutathione reductase activity and the total glutathione content (GSH + GSSG) were found when the gor gene was expressed in cells of the gor-mutant strain SG5 (SG5:pJIK1). Thus the activity of glutathione reductase is essential in order to maintain a high glutathione content. Furthermore, cells of the strain SG5: pJIK1 showed an increased sensitivity to methylviologen compared to cells of the gor mutant containing the vector pBR322 alone without the cloned gor gene insert (SG5:pBR322). In all experiments, the glutathione pool (GSH + GSSG) of bacterial cells was 90% reduced. In methylviologen-sensitive sodB mutant cells lacking iron superoxide dismutase activity (QC773:pBR322) overexpression of the cloned gor gene resulted in an elevated level of glutathione reductase activity which partially protected sodB mutant cells (QC773:pJIK1) against methylviologen toxicity. In sodB mutant cells expressing the gor gene (QC773:pJIK1) protection by glutathione reductase was, however, less effective than protection provided by expression of the iron superoxide dismutase gene (sodB gene) in these mutant cells (QC773:pJIK2). In sodA mutant cells lacking manganese superoxide dismutase activity but expressing the cloned gor gene (QC772:pJIK1) increased cellular glutathione reductase activity did not provide protection against methylviologen.

Cloning, Molecular↗