Silent information regulator sirtuin 1 ameliorates acute liver failure via the p53/glutathione peroxidase 4/gasdermin D axis

BACKGROUND Acute liver failure(ALF)has a high mortality with widespread hepatocyte death involving ferroptosis and pyroptosis.The silent information regulator sirtuin 1(SIRT1)-mediated deacetylation affects multiple biological processes,including cellular senescence,apoptosis,sugar and lipid metabolism,oxidative stress,and inflammation.AIM To investigate the association between ferroptosis and pyroptosis and the upstream regulatory mechanisms.METHODS This study included 30 patients with ALF and 30 healthy individuals who underwent serum alanine aminotransferase(ALT)and aspartate aminotransferase(AST)testing.C57BL/6 mice were also intraperitoneally pretreated with SIRT1,p53,or glutathione peroxidase 4(GPX4)inducers and inhibitors and injected with lipopolysaccharide(LPS)/D-galactosamine(D-GalN)to induce ALF.Gasdermin D(GSDMD)^(-/-)mice were used as an experimental group.Histological changes in liver tissue were monitored by hematoxylin and eosin staining.ALT,AST,glutathione,reactive oxygen species,and iron levels were measured using commercial kits.Ferroptosis-and pyroptosis-related protein and mRNA expression was detected by western blot and quantitative real-time polymerase chain reaction.SIRT1,p53,and GSDMD were assessed by immunofluorescence analysis.RESULTS Serum AST and ALT levels were elevated in patients with ALF.SIRT1,solute carrier family 7a member 11(SLC7A11),and GPX4 protein expression was decreased and acetylated p5,p53,GSDMD,and acyl-CoA synthetase long-chain family member 4(ACSL4)protein levels were elevated in human ALF liver tissue.In the p53 and ferroptosis inhibitor-treated and GSDMD^(-/-)groups,serum interleukin(IL)-1β,tumour necrosis factor alpha,IL-6,IL-2 and C-C motif ligand 2 levels were decreased and hepatic impairment was mitigated.In mice with GSDMD knockout,p53 was reduced,GPX4 was increased,and ferroptotic events(depletion of SLC7A11,elevation of ACSL4,and iron accumulation)were detected.In vitro,knockdown of p53 and overexpression of GPX4 reduced AST and ALT levels,the cytostatic rate,and GSDMD expression,restoring SLC7A11 depletion.Moreover,SIRT1 agonist and overexpression of SIRT1 alleviated acute liver injury and decreased iron deposition compared with results in the model group,accompanied by reduced p53,GSDMD,and ACSL4,and increased SLC7A11 and GPX4.Inactivation of SIRT1 exacerbated ferroptotic and pyroptotic cell death and aggravated liver injury in LPS/D-GalNinduced in vitro and in vivo models.CONCLUSION SIRT1 activation attenuates LPS/D-GalN-induced ferroptosis and pyroptosis by inhibiting the p53/GPX4/GSDMD signaling pathway in ALF.

Evaluation of Glutathione Peroxidase Enzymatic Activity in Seminal Plasma of Patients Treated at the Institute Pasteur in Cote d’Ivoire

Glutathione peroxidase (GPx) is an antioxidant that plays an important role in the maintenance of male fertility. The aim of this study was to compare the profile of enzymatic activity of glutathione peroxidase in the seminal plasma of normozoosperm and those of pathological sperm. Thus, the activity of glutathione peroxidase was determined in the seminal plasma of 20 normozoosperms, 9 azoosperms and 31 oligoasthenoteratozoosperms. It was 37.58 ± 3.14 U/L in normozoosperms, 39.39 ± 2.27 U/L in oligoasthenoteratozoosperms, and 29.77 ± 2.62 U/L in azoosperms. The mean GPx enzyme activity of normozoosperms did not differ significantly from that of oligoasthenoteratozoosperms and azoosperms. In contrast, comparison of enzyme activity between abnormal sperms gave a significant difference. This study showed that glutathione peroxidase enzymatic activity is not related to sperm quality.

Evaluation of combined detection of nuclear factor erythroid 2-related factor 2 and glutathione peroxidase 4 in primary hepatic carcinoma and preliminary exploration of pathogenesis

This study aims to analyze the clinical significance and mechanism of nuclear factor erythroid 2-related factor 2(NRF2)and glutathione peroxidase 4(GPX4)in primary hepatic carcinoma(PHC).Methods:The expression of NRF2 and GPX4 in peripheral blood of patients with PHC was determined to analyze the diagnostic value of the two combined for PHC.The prognostic significance of NRF2 and GPX4 was evaluated by 3-year followup.Human liver epithelial cells THLE-2 and human hepatocellular carcinoma cells HepG2 were purchased,and the expression of NRF2 and GPX4 in the cells was determined.NRF2 and GPX4 aberrant expression vectors were constructed and transfected into HepG2,and changes in cell proliferation and invasion capabilities were observed.Results:The expression of NRF2 and GPX4 in patients with PHC was higher than that in patients with LC or VH(p<0.05),and the two indicators combined was excellent in diagnosing PHC.Moreover,patients with high expression of NRF2 and GPX4 had a higher risk of death(p<0.05).In in vitro experiments,both NRF2 and GPX4 expression was elevated in HepG2(p<0.05).HepG2 activity was enhanced by increasing the expression of the two,vice versa(p<0.05).Conclusion:NRF2 and GPX4 combined is excellent in diagnosing PHC,and promotes the malignant development of PHC.

Glutathione peroxidase mimicry of diphenyl diselenide: Plausible contribution of proteins’ thiols

Organoseleniums are a class of compounds attracting attention across the globe owing to their Glutathione peroxidase(GPx)mimicry,which confers on them a strong antioxidant activity.Diphenyl diselenide(DPDS)is an Organoselenium whose GPx mimetic property has been suggested to rely on the oxidation of non-protein or protein thiols critical to the activities of some sulfhydryl enzymes.This study,therefore investigated the GPx mimic/antioxidant property of DPDS as well as the role of thiols of two key sulfhydryl enzymes,cerebral Na^(+)/K^(+)-ATPase(sodium pump)and hepatic delta-aminolevulinic acid dehydratase(δ-ALAD)in the GPx mimicry of DPDS.Albino Wistar rats were euthanized,and the liver and brain were removed and used to assay for the effect of DPDS on lipid peroxidation induced by two prooxidants[Fe2^(+)(10μM)and H2O2,(1 mM)]as well as the activities of the sulfhydryl enzymes.The results revealed that DPDS profoundly(P<0.05)counteracted Fe2^(+)and H2O2-induced lipid peroxidation in the rats’hepatic and cerebral tissues.Furthermore,the results of assay systems for lipid peroxidation and sodium pump revealed that DPDS inhibited Na^(+)/K^(+)-ATPase and lipid peroxidation in the brain tissue homogenates in the same reaction system.A similar result was obtained in the assay system for lipid peroxidation and hepaticδ-ALAD as DPDS simultaneously inhibited the enzyme’s activity and lipid peroxidation.This suggests that the GPx mimetic property of DPDS may be linked to the enzymes’loss of activity,which further validates the suggestions that the enzymes’inhibition,as well as the antioxidant action of DPDS,rely on the oxidation of critical thiols of the enzymes.However,the GPx mimicry of DPDS should be investigated in the presence of thiol-blocking or oxidizing agents in biological systems in order to further ascertain the role of protein thiols.

Expression and Chromosomal Mapping of Mouse Gpx2 Gene Encoding the Gastrointestinal Form of Glutathione Peroxidase, GPX-GI

GPX-GI is a cytosolic tetrameric Se-dependent glutathione peroxidase, similar in properties to GPX-1. Unlike the almost ubiquitous GPX-1, GPX-GI is mainly expressed in the epithelium of gastrointestinal tract. GPX-GI contributes to at least fifty percent of GPX activity in rodent small intestmal epithelium. The total GPX activity consists of at least 70% of selenium-dependent GPX activity in this compartment.By analyzing a panel of mouse mterspecies DNA from the Jackson Laboratory's backcross resource,we mapped Gpx2 gene to mouse chromosome 12 between D12Mit4 and D12Mit5, near the Ccs1 locus which contains a colon cancer susceptibility gene. A pseudogene, Gpx2-ps is mapped to mouse chromosome 7.Comparison of Gpx2 gene expression in three pairs of C57BL/6Ha and ICR/Ha mice which are respectively resistant and sensitive to dimethylhydrazine-induced colon cancer, we found a higher Gpx2 mRNA level in C57BL/6Ha colon than ICR/Ha colon. Interestingly, a lower level of GPX activity is found in the resistant strain of mice. Because GPX-1 has three times higher specific activity than GPX GI, our data suggest that the decreased GPX activity may result from a higher level of Gpx2 gene expression in those cells co-express GPx1 gene

Product of the Schistosoma mansoni Glutathione Peroxidase Gene is a Selenium ContainingPhospholipid Hydroperoxide Glutathione Peroxidase (PHGPx) Sharing MolecularWeight and Substrate Specificity WithIts Mammalian Counterpart

In the blood fluke Schistosoma mansoni a functionally active, monomeric, phospholipid hydroperoxide glutathione peroxidase (PHGPx) has been purified and characterized. This enzyme contains a catalytically active selenocysteine. The protein has been shown to be the product of a cloned gene, previously referred to as a glutathione peroxidase gene. S. mansoni PHGPx has been found 5 times more abundant in female than in male worm extract. As in vertebrate PHGPx, homology alignment indicates that the residues involved in the glutathione binding by the tetrameric cellular glutathione peroxidase are mutated in the S. mansoni enzyme. Thus, this aspect appears a landmark of the PHGPx-type of glutathione peroxidases,which might be of functional relevance

Phospholipid Hydroperoxide Glutathione Peroxidase(PHGPx): More Than an Antioxidant Enzyme?

The family of glutathione peroxidases encompasses, as far, three tetrameric glutathione'peroxidases (GPx) and the monomeric PHGPx. Although the overall homology between tetrameric enzymes and PHGPx is less than 30%, a pronounced similarity has been detected on clusters involved in the active site and a common catalytic triad (selenocysteine glutamine and tryptophan) has been defined by structural and kinetic data.A major peculiar feature of the reaction catalyzed by PHGPx is the possibility to accommodate large lipophilic substrates. This accounts for the observed dramatic antiperoxidant effect and the synergism with vitamin E.Moreover, the reduction of lipid hydroperoxides accounts also for the observed modulation of cycloxygenase and inhibition of 15-lipoxygenase.On the other hand, structural and kinetic data indicate that also the specificity of PHGPx for the donor substrate is not restricted to GSH and the recent observation the PHGPx binds to specific mitochondrial proteins, from which it is released by ionic strength and thiols, suggests a possible fole of this seleooenzyme'in catalyzing the specific oxidation of protein thiols,thus modulating the activity of cellular regulatory elements. on this light, the selenium mojety of PHGPx, reacting much faster that thiols with a peroxide, and then oxidizing specific protein thiols, would channel the oxidation toward protein targets, thus providing, by protein-protein interaction, the specificity of the redox transition

Novel Selenium-containing Human Single-chain Variable Fragment with Glutathione Peroxidase Activity from Computer-aided Molecular Design

In order to enhance the glutathione peroxidase（GPX） catalytic activity of the selenium-containing single-chain variable fragments（Se-scFv）, a novel human scFv was designed on the basis of the structure of human antibody and optimized via bioinformatics methods such as homologous sequence analysis, three-dimensional（3D） model building, binding-site analysis and docking. The DNA sequence of the new human scFv was synthesized and cloned into the expression vector pET22b（＋）, then the scFv protein was expressed in soluble form in Escherichia coli BL21（DE3） and purified by Ni2＋-immobilized metal affinity chromatography（IMAC）. The serine residue of scFv in the active site was converted into selenocysteine（Sec） with the chemical modification method, thus, the human Se-scFv with GPX activity was obtained. The GPX activity of the Se-scFv protein was characterized. Compared with other Se-scFv, the new human Se-scFv showed similar efficiency for catalyzing the reduction of hydrogen peroxide by glutathione. It exhibited pH and temperature dependent catalytic activity and a typical ping-pong kinetic mechanism.

Cloning of catalase and expression patterns of catalase and selenium-dependent glutathione peroxidase from Exopalaemon carinicauda in response to low salinity stress

Catalase （CAT） and selenium-dependent glutathione peroxidase （Se-GPx） play a vital role in protecting organisms against various oxidative stresses by eliminating H202, The objective of this paper is to evaluate the roles of these antioxidant molecules in the ridgetail white prawn Exopalaemon carinicauda in response to low salinity stress. A complementary DNA （cDNA） containing the complete coding sequence of CAT was cloned from the hepatopancreas using reverse-transcription polymerase chain reaction （RT-PCR） and rapid amplification of cDNA ends. The full-length cDNA of CAT （2 649 bp） contains a 5＇-untranslated region （UTR） of 78 bp, a 3＇- UTR of 1 017 bp, with a poly （A） tail, and an open reading frame of 1 554 bp encoding a 517-amino-acid polypeptide with predicted molecular mass of 58.46 kDa and estimated isoelectric point of 6.64. This CAT sequence contained the proximal active site signature （60FDRERIPERWHAKGAG76）, proximal heme-ligand signature sequence （350RLFSYPDTH358） and three catalytic amino acid residues （His71, Asn144 and Tyr354）. Sequence comparison showed that the CAT deduced amino acid sequence of E. carinicauda shared 68%-92% of identities with those of other species. Quantitative real-time PCR analysis revealed that CAT mRNA was widely expressed in the hepatopancreas （highest）, hemocyte, eyestalk, heart, gill, muscle, ovary and stomach. Under low salinity stress, CAT and GPx mRNA expression levels both in the gill and hepatopancreas increased significantly at the first 48 h and 6 h respectively, indicating a tissue- and time-dependent antioxidant response in E. carinicauda. All these results indicate that E. carinicauda CAT is a member of the CAT family and might be involved in the acute response against low salinity stress.

Glutathione Peroxidase Revisited—Simulation of the Catalytic Cycle by Computer-Assisted Molecular Modelling

Glutathione peroxidase, the first example of selenoproteins identified in mammals, was subjected to force field calculations and molecular dynamics in order to enable a clearer comprehension of enzymatic selenium catalysis. Starting from the established X-ray structure of bovine GPX, all kinetically defined intermediates and enzyme substrate complexes were modelled. The models thus obtained support the hypothesis that the essential steps of the catalysis are three distinct redox changes of the active site selenium which, in the ground state, presents itself at the surface of selenoperoxidases as the center of a characteristic triad built by selenocysteine, glutarnine and tryptophan. In GPX, four arginine residues and a lysine residue provide an electrostatic architecture which, in each reductive step, directs the donor substrate GSH towards the catalytic center in such a way that 1ts sulfhydryl group must react with the selenium moiety. To this end, different equally efficient modes of substrate binding appear possible. The models are consistent with substrate specificity data, kinetic pattern and other functional characteristics of the enzyme. Comparison of molecular models of GPX with those of other members of the GPX superfamily reveals that the cosubstrate binding mechanisrns are unique for the classical type of cytosolic glutathione peroxidases but cannot operate e. g. in plasma GPX and phospholipid hydroperoxide GPX. The structural differences between the selenoperoxidases, shown to be relevant to their specificities, are discussed in terms of functional diversification within the GPX superfamily

Artesunate Effect on Schistosome Thioredoxin Glutathione Reductase and Cytochrome c Peroxidase as New Molecular Targets in Schistosoma mansoni-infected Mice

Objective To investigate the possible effect of artesunate （ART） on schistosome thioredoxin glutathione reductase （TGR） and cytochrome c peroxidase （CcP） in Schistosoma mansoni-infected mice. Methods A total of 200 laboratory bred male Swiss albino mice were divided into 4 groups （50 mice in each group）. Group I： infected untreated group （Control group） received a vehicle of 1% sodium carbonyl methylcellulose （CMC-Na）; Group II： infected then treated with artesunate; Group III infected then treated with praziquantel, and group IV： infected then treated with artesunate then praziquantel. Adult S. mansoni worms were collected by Animal Perfusion Method, tissue egg counted, TGR, and CcP mRNA Expression were estimated of in $. mansoni adult worms by semi-quantitative rt-PCR. Results Semi-quantitative rt-PCR values revealed that treatment with artesunate caused significant decrease in expression of schistosome TGR and CcP in comparison to the untreated group. In contrast, the treatment with praziquantel did not cause significant change in expression of these genes. The results showed more reduction in total worm and female worm count in combined ART-PZQ treated group than in monotherapy treated groups by either ART or PZO, Moreover, complete disappearance （100%） of tissue eggs was recorded in ART-PZQ treated group with a respective reduction rate of 95.9% and 68.4% in ART- and PZQ-treated groups. Conclusion The current study elucidated for the first time that anti-schistosomal mechanisms of artesunate is mediated via reduction in expression of schistosome TGR and CcP. Linking these findings, addition of artesunate to praziquantel could achieve complete cure outcome in treatment of schistosomiasis.

Glutathione peroxidase activity in cell cultures from different regions of human epididymis

Aim: To study the secretory activity and androgen regulation of glutathione peroxidase (GPx) in epithelial cell cultures from human epididymis. Methods: Tissue was obtained from patients undergoing therapeutic orchidectomy for prostatic cancer. Epithelial cell cultures were obtained from the caput, corpus and cauda epididymides. Enzymatic activity was measured in conditioned media by colorimetric methods in absence or presence of 1, 10 or 100 nrnoI.L^(-1) testosterone. The effect of 1 μmol.L^(-1) flutamide was also evaluated. Results: GPx activity was higher in cultures from corpus and cauda than caput epididymidis. The presence of different concentrations of testosterone increase enzyme activity in cell cultures from all epididymal regions. Addition of flutamide reverses the androgen dependent increase of GPx activity. Conclusion: GPx activity is secreted from human epididymal cells in a region dependent manner and is regulated by androgens.

Selenium Regulation of Selenium-dependent Glutathione Peroxidases in Animals and Transfected CHO Cells

Glutathione peroxidase (GPX1) was the first identified selenium-dependent enzyme, and this enzyme has been most useful as a biochemical indicator of selenium (Se) status and the parameter of choice for determining Se requirements. We have continued to study Se regulation of GPX1 to better understand the underlying mechanism and to gain insight into how cells themselves regulate nutrient status. In progressive Se deficiency in rats, GPX1 activity,protein and mRNA all decrease in a dramatic, coordinated and exponential fashion such that Se-deficient GPX1 mRNA levels are 6-15% of Sexadequate levels. mRNA levels for other Sedependent proteins are far less decreased in the same animals. The mRNA levels for a second Se-dependent peroxidase, phospholipid hydroperoxide glutathione peroxidase (GPX4 ), are little affected by Se deficiency, demonstrating that Se regulation of GPX1 is unique. Se regulation of GPX1 activity in growing male and female rats shows that the Se requirernent is 100 ng/g diet, based on liver GPX1 activity; use of GPX1 mRNA as the parameter indicates that the Se requirement is nearer to 50 ng Se/g diet in both male and female rats. This approach will readily detect an altered dietary Se requirement, as shown by the incremental increases in dietary Se requirement by 150, 100 or 50 ng Se/g diet in Seudeficient rat pups repleted with Se for 3, 7 or 14 d, respectively. Studies with CHO cells stably transfected with recombinant GPX1 also show that overexpression of GPX1 does not alter the minimum level of media Se necessary for Se-adequate levels of GPX1 activity or mRNA. We hypothesize that classical GPX1 has an integral biological role in the mechanism used by cells to regulate Se status,making GPX1 an especially useful and effective parameter for determining Se requirements in animals

Glutathione peroxidase, superoxide dismutase and catalase activities in children with chronic hepatitis

The advantages of measuring hepatic oxidative status in liver biopsy are that it helps in diagnosis of hepatic dysfunction, reflects the degree of deterioration in the liver tissues, and helps to determine the severity of hepatic injury. We aimed to study the oxidative stress state in children with chronic hepatitis by using indirect approach in which antioxidant enzymes such as glutathione peroxidase (GPX), superoxide dismutase (SOD) and catalase (CAT) are determined in the liver tissue. The present study included 21 children and adolescents (12 males, 9 females) suffering from chronic hepatitis. Patients were selected from the Hepatology Clinic, New Children’s Hospital, Cairo University from November 2006 till 2009 and compared with a group of 7 children who happened to have incidental normal liver biopsy. Children with chronic hepatitis had mean age 8.12 ± 1.15 years. It was further subdivided into 2 subgroups: chronic viral heaptitis (n = 13) and cryptogenic hepatitis (n = 8). GPX, SOD and CAT levels were measured in fresh liver tissue (cell free homogenates) using ELISA. In chronic hepatitis group;there was a significant increase in the hepatic GPX activity (38.59 ± 35.82 nmol/min/ml) as compared to the control group (10.62 ± 6.68 nmol/min/ml). Also a significant correlation was observed between SOD and both ALT (r = 0.87, p < 0.05) and AST (r = 0.74, p < 0.05). GPX correlated with ALT (r = 0.80, p < 0.05) level in the chronic viral hepatitis subgroup. Our findings suggest that oxidative stress could play a role in the pathogenesis of chronic hepatitis. These preliminary results are encouraging to conduct more extensive clinical studies combining antioxidant therapy with various treatments.

Effect of 2-Selenium Bridged β-Cyclodextrin,Glutathione Peroxidase Mimic on Stroke of Stroke-prone Spontaneously Hypertensive Rats

To investigate the treatment effect of 2-selenium bridged β -cyclodextrin(2-SeCD),a GPX mimic,on the stroke of stroke-prone spontaneously hypertensive rats(SHRSP),fifty-two SHRSP of 8-week old were randomly divided into four groups A,B,C and control group D. The rats of groups A,B,C and D were given 1.0%-1.5% NaCl mass fraction as drinking fluid. After onset of stroke,groups A,B and C were given \{orally\} 16.05,160.5 and 1605 mg·kg -1 ·day -1 of 2-SeCD,respectively,and group D was given water for \{2 weeks.\} The clinical score of stroke,systolic blood pressure(SBP),survival time of rats were recorded and the histopathologic examinations of their brain and carotid artery were made after decapitation. The clinical scores of stroke after treatment with 160.5 mg·kg -1 ·day -1 (Group B) and 1605 mg·kg -1 ·day -1 (Group C) of 2-SeCD are 2.55±0.98 and 1.98±0.79,respectively,those are obviously lower than that of group D(3.41±0.83,p<0.01). The survival days in group B(10.0±8.6) and group C(14.4±7.9) are longer than that for group D(4.7±2.9,p<0.01). The electron microscope study showed that the endothelium of carotid artery was near to normal in group B and group C,while it was seriously injured in control group D and mildly injured in group A. 2-SeCD may effectively be used to treat the stroke for SHRSP.

Hydrophobic Pocket Modification and Humanized Catalytic Antibodies with Glutathione Peroxidase Activity(Ⅰ)——Preparation and Characterization of Haptenes and Conjugates

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Synthesis and Kinetics of a Novel Mimic with Glutathione Peroxidase Activity—Tellurium-containing Hyaluronic Acid (TeHA)

A novel mimic was synthesized by modifying hyaluronic acid （HA） with tellurium, whose function is similar to that of glutathione peroxidase （GPX）. The structure of TeHA was characterized by means of IR and NMR, the target-Te was located at -CH2OH of the N-acetyl-D- glucosamine of HA. The H202 reducing activity of TeHA, by glutathione （GSH）, was 163.6 U/μmol according to Wilson＇s method. In contrast to other mimics, TeHA displayed the highest activity. Moreover, TeHA accepted many hydroperoxides as its substrates, such as H2O2, cumenyl hydroperoxide （CuOOH） and tert-butyl hydroperoxide （t-BuOOH）, and CuOOH was the optimal substrate of TeHA. A ping-pong mechanism was observed in the steady-state kinetic studies of the reactions catalyzed by TeHA.

Changes of Selenium Metabolism Glutathione Peroxidase Activity and Lipid Peroxides Content in Severely Scalding-injured Rats

The changes of sclenium metabolism, glutathione peroxidase activity and lipid peroxidescontent in the tissues of rats suffering from 30% TBSA full thickness scalding were observed in thefirst 7 days after injury. It was found that selenium content in the rat tissues decreased remarkably af-ter injury, which in turn resulted in serious reduction of glutathione peroxidasc activity and significantincrease of lipid peroxides in the scrum, crythrocytcs and liver. However the muscular tissue showedno significant changes. These facts imply that after burn injury, the body is in a state of selenium deficiency, the lossof selenium might be responsible for the reduction of anti - peroxidation ability of glutathioneperoxidase, and conscqucntly there is an increase of lipid peroxides in the tissues. Only the musculartissue is insensitive to lipid peroxidation. It is believed that the reduction of anti-peroxidation abilityof glutathione peroxidasc after bum injury might be one of the main causes to intensify, the injury re-suiting from free radicals.

Synthesis and Characterization of Specific Haptens Used to Generate Abzyme with Glutathione Peroxidase Activity

Glutathione was modified selectively by 2,4 dinitrochlorobenzene,giving S substituted dinitrophenyl glutathione(GSH S DNP).GSH S DNP was further esterified by iso butanol,hexanol,cyclohexanol and benzyl alcohol.Four haptens used to generate abzyme with glutathione peroxidase(GPX)activity were synthesized.They are GSH DNP biesters:GSH DNP di iso butyl ester(GSH DNP IBU),GSH DNP bihexyl ester(GSH DNP HE),GSH DNP bicyclohexyl ester(GSH DNP CH),GSH DNP bibenzylmethyl ester(GSH DNP BE).The structures of the haptens were characterized by means of elemental analysis,IR and 1H NMR.

Urea-induced Inactivation and Unfolding of Recombinant Phospholipid Hydroperoxide Glutathione Peroxidase from Oryza sativa

Phospholipid hydroperoxide glutathione peroxidase is an antioxidant enzyme that has the highest capability of reducing membrane-bound hydroperoxy lipids as compared to free organic and inorganic hydroperoxides amongst the glutathione peroxidases.In this study,urea-induced effects on the inactivation and unfolding of a recombinant phospholipid hydroperoxide glutathione peroxidase（PHGPx）from Oryza sativa were investigated by means of circular dichroism and fluorescence spectroscopy.With the increase of urea concentration,the residual activity of OsPHGPx decreases correspondingly.When the urea concentration is above 5.0 mol/L,there was no residual activity.In addition,the observed changes in intrinsic tryptophan fluorescence,the binding of the hydrophobic fluorescence probe ANS,and the far UV CD describe a common dependence on the concentration of urea suggesting that the conformational features of the native OsPHGPx are lost in a highly cooperative single transition.The unfolding process comprises of three zones：the native base-line zone between 0 and 2.5 mol/L urea,the transition zone between 2.5 and 5.5 mol/L urea,and the denatured base-line zone above 5.5 mol/L urea.The transition zone has a midpoint at about 4.0 mol/L urea.