Properties Of Glutathione Reductase Research Articles

Catalytic properties of glutathione reductase from liver at norm and toxic hepatitis

Homogeneous preparations of liver glutathione reductase (GR, EC 1.6.4.2.), obtained from control rats and animals with toxic hepatitis, catalytic properties of this enzyme have been investigated. A number of the enzyme properties did not change under conditions of hepatitis. These included electrophoretic mobility (R(f) = 0.23 +/- 0.01), molecular mass (104 +/- 5.20 kDa), pH-optimum (7.4 +/- 0.37). There was similarity in pK values of functional groups. At the same time, decrease in affinity of enzyme to a substrate and coenzyme and occurrence substrate-linked inhibition was observed under conditions of this pathology. There were some differencies in regulation of GR activity by metabolites of tricarboxylic acid cycle.

Purification and properties of glutathione reductase from liver of the anoxia-tolerant turtle, Trachemys scripta elegans

Glutathione reductase (GR) is a homodimeric flavoprotein that catalyzes the reduction of oxidized glutathione (GSSG) using NADPH as a cofactor. The enzyme is a major component of cellular defense mechanisms against oxidative injury. In this study, GR was purified from the liver of the anoxia-tolerant turtle, Trachemys scripta elegans. The overall fold purifications were 13.3- and 12.1-fold with final specific activities of 5.5 and 1.44 U/mg of protein for control and anoxic turtle GR, respectively. SDS-PAGE of purified turtle liver GR showed a single protein band at approximately 55 kDa. Reverse phase HPLC of turtle GR revealed a single peak that had the same retention time as yeast GR. No new isoform of GR was detected in liver of T. s. elegans during anoxia. The K (m) values of turtle GR for GSSG and NADPH was 44.6 and 6.82 microM, respectively, suggesting a substantially higher affinity of turtle GR toward GSSG than most other vertebrates. Unlike other human GR, NADP(+ )did not inhibit turtle GR activity. The activation energy of turtle GR, calculated from the slope of the Arrhenius plot, was 32.2 +/- 2.64 kJ/mol. Turtle GR had high activity under a broad pH range (having activity between pHs 4 and 10; optimal activity at pH 6.5) and the enzyme maintains activity under the pH drop that occurs under anoxic conditions. The high affinity of turtle GR suggests that turtles have high redox buffering capacity of tissues to protect against oxidative stress encountered during anoxia/reoxygenation.

Instantaneous and Developmental Effects of Low Temperature on the Catalytic Properties of Antioxidant Enzymes in Two Zea Species

When Zea mays cv. LG11 plants were grown 14˚C(close to the lower thermal limit for leaf expansion), three of the five enzymes of the active oxygen scavenging cycle (Halliwell-Asada Pathway) showed changes in total leaf activity compared with growth at 25˚C. Two of theseenzymes, ascorbate peroxidase (APX) and glutathione reductase (GTR), were selected for further investigation. The effects of assay temperature on threekinetic parameters (Vmax,Km,Vmax/Km) were determined inextracts from Z. mays and compared with extracts fromits low temperature tolerant relative, Z. diploperennisIltis, Doebley & Guzman. The kinetic power(Vmax/Km) was determinedbecause the Km alone may not be a useful predictor of anenzyme’s effectiveness in situ. The decrease inthe kinetic power of APX on lowering the temperature to 5ºC was muchsmaller in Z. diploperennis thaninZ. mays. This suggests that theZ. diploperennis APX is better able to removeH2O2 at severely reducedtemperatures than is APX from Z. mays.Z. diploperennis had a twofold greater ascorbate poolthan the chilling-susceptible Z. mays. Only minordifferences were seen in the kinetic properties of GTR and the size of theglutathione pool between the genotypes.

The purification and properties of glutathione reductase from the cestode Moniezia expansa

Glutathione reductase has a central role in glutathione metabolism and as such is a potential target for chemotherapy. The aim of the work was to purify and characterise glutathione reductase from the cestode Moniezia expansa and to compare the properties of the helminth enzyme with its mammalian counterpart. The enzyme was purified by a combination of anion exchange and affinity chromatography and further characterized by chromatofocusing and gel electrophoresis. Analysis revealed a single isoenzyme of glutathione reductase in Moniezia expansa, with a pI of 5.8. The enzyme was a homodimer of native molecular weight 114 kDa, subunit weight 63 kDa. Enzyme activity was affected by buffer concentration and the presence of monovalent sodium salts. The pH optimum was 7.4 with NADPH as cofactor and 5 with NADH. The K m a for oxidized glutathione was 76 μM and for NADPH and NADH, 21 and 350 μM respectively. In addition to oxidized glutathione only the mixed disulphide between CoA and glutathione (CoASSG) showed any significant activity as substrate. The cestode enzyme was inhibited by a variety of compounds including arsonic derivatives, 2,4,6 trinitrobenzene sulfonate 1,3-bis (2-chlorethyl)-1-nitrosourea and oxidized glutathione. In conclusion the glutathione reductase of M. expansa resembles the mammalian enzyme in its general physical properties and its substrate and inhibitor profile. However, the parasite enzyme shows an unusually high activity with the mixed disulphide of coenzyme A and glutathione (CoASSG) and appears to be more sensitive to inhibition by sodium ions.

Synthesis and properties of glutathione reductase in stressed peas

We have subjected peas (Pisum sativum L.) to four different oxidative stresses: cold conditions (4 °C) in conjunction with light, treatment with paraquat, fumigation with ozone, and illumination of etiolated seedlings (greening). In crude extracts of leaves from stressed plants, an increase (up to twofold) in activity of glutathione reductase (GR) was observed which was consistent with previous reports from several laboratories. In all cases, except for ozone fumigation, the increase in activity was not due to an elevation in the steady-state levels of GR protein. None of the applied stresses had any effect on steady-state levels of GR mRNA. In contrast to the small increase in GR activity, the K m of GR for glutathione disulphide showed a marked decrease when determined for extracts of stressed leaves, compared with that from unstressed plants. This indicates that GR from stressed plants has an increased affinity for glutathione disulphide. The profile of GR activity bands fractionated on non-denaturing acrylamide gels varied for extracts from differently stressed leaves and when compared with GR from unstressed plants. The changes in GR-band profiles and the alteration in the kinetic properties are best explained as changes in the isoform population of pea GR in response to stress.

Properties of glutathione reductase from chloroplasts and roots of pea

In Pisum sativum, about 90% of the glutathione in leaf and root is in the reduced form. GSSG reductase has been purified from chloroplasts and roots. The two enzymes had similar M,s, but differed in pH optimum and sensitivity to inhibition by zinc, copper and ferrous ions. In comparison with the oxidized form, the reduced form of the enzymes had a much greater temperature instability, and was inhibited by N-ethyl maleimide.

Purification and properties of glutathione reductase from the cyanobacterium Anabaena sp. strain 7119.

An NADPH-glutathione reductase (EC 1.6.4.2) has been purified 6,000-fold to electrophoretic homogeneity from the filamentous cyanobacterium Anabaena sp. strain 7119. The purified enzyme exhibits a specific activity of 249 U/mg and is characterized by being a dimeric flavin adenine dinucleotide-containing protein with a ratio of absorbance at 280 nm to absorbance at 462 nm of 5.8, a native molecular weight of 104,000, a Stokes radius of 4.13 nm, and a pI of 4.02. The enzyme activity is inhibited by sulfhydryl reagents and heavy-metal ions, especially in the presence of NADPH, with oxidized glutathione behaving as a protective agent. As is the case with the same enzyme from other sources, the kinetic data are consistent with a branched mechanism. Nevertheless, the cyanobacterial enzyme presents three distinctive features with respect to that isolated from non-photosynthetic organisms: (i) absolute specificity for NADPH, (ii) an alkaline optimum pH value of ca. 9.0, and (iii) strong acidic character of the protein, as estimated by column chromatofocusing. The kinetic parameters are very similar to those found for the chloroplast enzyme, but the molecular weight is lower, being comparable to that of non-photosynthetic microorganisms. A protective function, analogous to that assigned to the chloroplast enzyme, is suggested.

Purification and properties of glutathione reductase from hepatopancreas of Mytilus edulis L.

1. 1. The enzyme glutathione reductase (GR) from hepatopancreas of Mytilus edulis L. was purified 80-fold by extraction, fractionated precipitation with ammonium sulphate, ion-exchange chromatography on DEAE-Sephadex, absorption chromatography on hydroxyapatite and gel-filtration through Sephadex G-200. 2. 2. The optimal pH was 7.5 and the K m for GSSG and NADPH were respectively 0.065 and 0.0041 mM. 3. 3. Glutathione reductase is rapidly activated by preincubation at 40°C either alone or with 1 mM GSSG. After 2 hr incubation the activity is 150% of the initial value. At 60°C the enzyme is rapidly inactivated, whether incubated alone or in the presence of 0.1 mM NADP +. One mM GSSG protects the activity of the enzyme to some extent. At 20°C glutathione reductase is inactivated by NADPH and GSH. 4. 4. NaCl and KCl at concentrations close to those they have in seawater are activators. Contrary to the findings of other authors zinc sulphate is also a strong activator of enzyme at 0.2 mM concentration.

The Isolation and Properties of Glutathione Reductase from Human Erythrocytes

Conference Article| October 01 1974 The Isolation and Properties of Glutathione Reductase from Human Erythrocytes DAVID J. WORTHINGTON; DAVID J. WORTHINGTON 1Department of Biochemistry, University College London, Gower Street, London WC1E 6BT, U.K. Search for other works by this author on: This Site PubMed Google Scholar MICHAEL A. ROSEMEYER MICHAEL A. ROSEMEYER 1Department of Biochemistry, University College London, Gower Street, London WC1E 6BT, U.K. Search for other works by this author on: This Site PubMed Google Scholar Biochem Soc Trans (1974) 2 (5): 927–929. https://doi.org/10.1042/bst0020927 Views Icon Views Article contents Figures & tables Video Audio Supplementary Data Peer Review Share Icon Share Facebook Twitter LinkedIn MailTo Cite Icon Cite Get Permissions Citation DAVID J. WORTHINGTON, MICHAEL A. ROSEMEYER; The Isolation and Properties of Glutathione Reductase from Human Erythrocytes. Biochem Soc Trans 1 October 1974; 2 (5): 927–929. doi: https://doi.org/10.1042/bst0020927 Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentAll JournalsBiochemical Society Transactions Search Advanced Search This content is only available as a PDF. © 1974 Biochemical Society1974 Article PDF first page preview Close Modal You do not currently have access to this content.