Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:1.11.1.7 (peroxidase)
65,474 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The activities of various peroxide-metabolizing enzymes were determined in homogenates of human liver excisions. The specific activity of selenium-dependent glutathione peroxidase was 41.1 +/- 23.7 (S.D.) mU/mg protein; non-selenium glutathione peroxidase showed a activity of 30.5 +/- 14.0 mU/mg protein. The catalase and superoxide dismutase concentrations were 4.72 +/- 0.58 and 1.87 +/- 0.68 microgram/mg protein, respectively. Total glutathione amounted to 12.9 +/- 7.4 nmol/mg. Malondialdehyde formation, used as the basis for the determination of lipid hydroperoxides, was 0.32 +/- 0.14 nmol/mg. The data indicate much lower enzyme and substrate levels compared to rats and mice. A positive correlation of r = 0.48 +/- 0.31 was found between the glutathione level and selenium-dependent peroxidase. Selenium-dependent and non-selenium-glutathione peroxidase correlate negatively (r = -0.71 +/- 0.18); superoxide dismutase concentration and lipid-hydroperoxides are also related by a negative correlation coefficient of r = 0.47 +/- 0.31. These data stress the major hepatoprotective role of these systems in human liver.
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PMID:[The activity of the peroxide-metabolizing system in human liver (author's transl)]. 45 83

Strenuous physical exercise in the form of swimming in female albino rats increased the oxidative reactions, probably leading to the generation of oxy-free radicals in the lung tissue. Free radical-mediated lipid peroxidation measured in the form of lipid peroxides increased in the pulmonary tissue in response to exhaustive exercise, indicating such a possibility. Dietary supplementation of vitamin E (Vit.E) and selenium (Se) for a period of 12 weeks reduced the oxidative reactions and the ensuing lipid peroxidation in the pulmonary tissue. Physical exercise in control animals induced the activity of superoxide dismutase (SOD), the superoxide anion radical (O2-.) quencher. However, the SOD levels in nutrient-fed animals at rest and after exercise remained well below the control levels, indicating the decreased generation of oxy-free radicals in them. Similarly, selenium-dependent glutathione peroxidase (Se-GSH Px), the enzyme involved in the reduction of organic and inorganic peroxides, and glutathione S- transferase (GST), the multifunctional protein involved in the detoxification of a number of xenobiotics, were increased in response to exercise in control animals, but were significantly decreased in nutrient-fed animals upon exercise. The induction of GST seems to be more towards the peroxidase activity of GST, i.e., non-selenium glutathione peroxidase (Non-Se-GSH Px), which is primarily involved in the reduction of endoperoxides. The studies thus indicate the induction of oxidative stress in the pulmonary tissue upon exhaustive physical exercise and the effectiveness of vit.E and Se independently and more so in combination in combating the exercise-induced oxidant stress.
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PMID:Exercise-induced oxidant stress in the lung tissue: role of dietary supplementation of vitamin E and selenium. 161 Mar 86

We have isolated a novel secretory 28-kDa protein which is an abundant component of the rat olfactory mucosa. The partial sequence of the 28-kDa protein has been determined. The amino acid sequence of the 28-kDa protein is similar to that of non-selenium glutathione peroxidase from bovine ciliary body. The 28-kDa protein catalyzed decomposition of the hydrogen peroxide as well as organic hydroperoxides by reduced glutathione and seems to be a member of the glutathion peroxidase family.
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PMID:Novel 28-kDa secretory protein from rat olfactory epithelium. 864 18

Keratinocyte growth factor is a potent and specific mitogen for different types of epithelial cells, including keratinocytes of the skin. Furthermore, it has been implicated in morphogenetic processes of several organs. To further define the mechanisms of KGF action in the skin, we attempted to identify genes which are regulated by KGF in keratinocytes. Using the differential display RT-PCR technology, a gene was identified which was strongly induced in these cells by treatment with KGF but not with serum growth factors or pro-inflammatory cytokines. Molecular cloning of the full-length cDNA revealed a strong homology of the corresponding gene product with a bovine non-selenium glutathione peroxidase. Upon transfection of COS cells with the full-length cDNA, a 27 kD cytoplasmic protein was obtained which had the expected size of glutathione peroxidase. Expression of the novel gene was detected in normal human skin and at particularly high levels in psoriatic skin, indicating a possible in vivo function of the protein in this tissue. Identification of a peroxidase as a KGF-regulated gene suggests that prevention from oxygen toxicity is a novel and specific mechanism of KGF action.
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PMID:The human homologue of a bovine non-selenium glutathione peroxidase is a novel keratinocyte growth factor-regulated gene. 905 Sep 90

A new type of peroxidase enzyme, named thioredoxin peroxidase (TPx), that reduces H2O2 with the use of electrons from thioredoxin and contains two essential cysteines was recently identified. TPx homologs, termed peroxiredoxin (Prx), have also been identified and include several proteins, designated 1-Cys Prx, that contain only one conserved cysteine. Recombinant human 1-Cys Prx expressed in and purified from Escherichia coli has now been shown to reduce H2O2 with electrons provided by dithiothreitol. Furthermore, human 1-Cys Prx transiently expressed in NIH 3T3 cells was able to remove intracellular H2O2 generated in response either to the addition of exogenous H2O2 or to treatment with platelet-derived growth factor. The conserved Cys47-SH group was shown to be the site of oxidation by H2O2. Thus, mutation of Cys47 to serine abolished peroxidase activity. Moreover, the oxidized intermediate appears to be Cys-SOH. In contrast to TPx, in which one of the two conserved cysteines is oxidized to Cys-SOH and then immediately reacts with the second conserved cysteine of the second subunit of the enzyme homodimer to form an intermolecular disulfide, the Cys-SOH of 1-Cys Prx does not form a disulfide. Neither thioredoxin, which reduces the disulfide of TPx, nor glutathione, which reduces the Cys-SeOH of oxidized glutathione peroxidase, was able to reduce the Cys-SOH of 1-Cys Prx and consequently could not support peroxidase activity. Human 1-Cys Prx was previously shown to exhibit a low level of phospholipase A2 activity at an acidic pH; the enzyme was thus proposed to be lysosomal, and Ser32 was proposed to be critical for lipase function. However, the mutation of Ser32 or Cys47 has now been shown to have no effect on the lipase activity of 1-Cys Prx, which was also shown to be a cytosolic protein. Thus, the primary cellular function of 1-Cys Prx appears to be to reduce peroxides with the use of electrons provided by an as yet unidentified source; the enzyme therefore represents a new type of peroxidase.
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PMID:Characterization of a mammalian peroxiredoxin that contains one conserved cysteine. 949 58

This report provides definitive evidence that the protein 1-Cys peroxiredoxin is a bifunctional ("moonlighting") enzyme with two distinct active sites. We have previously shown that human, rat, and bovine lungs contain an acidic Ca(2+)-independent phospholipase A(2) (aiPLA(2)). The cDNA encoding aiPLA(2) was found to be identical to that of a non-selenium glutathione peroxidase (NSGPx). Protein expressed using a previously reported E. coli construct which has a His-tag and 50 additional amino acids at the NH(2) terminus, did not exhibit aiPLA(2) activity. A new construct which contains the His-tag plus two extra amino acids at the COOH terminus when expressed in Escherichia coli generated a protein that hydrolyzed the sn-2 acyl chain of phospholipids at pH 4, and exhibited NSGPx activity with H(2)O(2) at pH 8. The expressed 1-Cys peroxiredoxin has identical functional properties to the native lung enzyme: aiPLA(2) activity is inhibited by the serine protease inhibitor, diethyl p-nitrophenyl phosphate, by the tetrahedral mimic 1-hexadecyl-3-trifluoroethylglycero-sn-2-phosphomethanol (MJ33), and by 1-Cys peroxiredoxin monoclonal antibody (mAb) 8H11 but these agents have no effect on NSGPx activity; NSGPx activity is inhibited by mercaptosuccinate and by 1-Cys peroxiredoxin mAb 8B3 antibody which have no effect on aiPLA(2) activity. Mutation of Ser(32) to Ala abolishes aiPLA(2) activity, yet the NSGPx activity remains unaffected; a Cys(47) to Ser mutant is devoid of peroxidase activity but aiPLA(2) activity remains intact. These results suggest that Ser(32) in the GDSWG consensus sequence provides the catalytic nucleophile for the hydrolase activity of aiPLA(2), while Cys(47) in the PVCTTE consensus sequence is at the active site for peroxidase activity. The bifunctional catalytic properties of 1-Cys peroxiredoxin are compatible with a simultaneous role for the protein in the regulation of phospholipid turnover as well as in protection against oxidative injury.
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PMID:1-Cys peroxiredoxin, a bifunctional enzyme with glutathione peroxidase and phospholipase A2 activities. 1089 23

Six distinct peroxiredoxin (Prx) proteins (Prx I-VI) from distinct genes have been identified in mammalian tissues. Prxs are members of a group of peroxidases that have conserved reactive cysteine residue(s) in the active site(s). An immediate physiological electron donor for the peroxidase catalysis for five Prx proteins (Prx I-V) has been identified as thioredoxin (Trx), but that for Prx VI (1-Cys Prx) is still unclear. To identify an immediate electron donor and a binding protein for Prx VI, we performed a Prx VI protein overlay assay. A 20-kDa binding protein was identified by the Prx VI protein overlay assay with flow-through fractions from a High-Q column with rat lung crude extracts. Using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF) and MS-Fit, we identified the 20-kDa Prx VI-binding protein as a cyclophilin A (CyP-A). The binding of recombinant human CyP-A (hCyP-A) to Prx VI was confirmed by using the hCyP-A protein overlay assay and Western immunoblot analysis with hCyP-A-specific antibodies. hCyP-A enhanced the antioxidant activity of Prx VI, as well as the other known mammalian Prx isotypes. hCyP-A supported antioxidant activity of Prx II and Prx VI both against thiol (dithiothreitol)-containing metal-catalyzed oxidation (MCO) systems and ascorbate-containing MCO systems. Prx II was reduced by hCyP-A without help from any other reductant, and the reduction was cyclosporin A-independent. These results strongly suggest that CyP-A not only binds to Prx proteins but also supports its peroxidase activity as an immediate electron donor. In addition, Cys(115) and Cys(161) of hCyP-A were found to be involved in the activation and the reduction of Prx.
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PMID:Cyclophilin a binds to peroxiredoxins and activates its peroxidase activity. 1139 Mar 85

We have identified the 2-Cys peroxiredoxin (PfPrx-1) from the human malaria parasite Plasmodium falciparum. The PfPrx-1 showed the highest identity at amino acid level to the type II Prx among the currently known six subfamilies of mammalian Prx. The sequence identity between the PfPrx-1 and the previously reported 1-Cys Prx of P. falciparum (PfPrx-2), which corresponded to mammalian type VI Prx, was 25%. This suggests that the parasite possesses two Prx subfamilies. The PfPrx-1 showed significant sequence similarities with those of 2-Cys peroxiredoxins of plants in the BLASTX search. This may reflect the consequences of a genetic transfer from an algal endosymbiont to the parasite nucleus during evolution. The recombinant PfPrx-1 protein (rPfPrx-1) was expressed as a histidine fusion protein in Escherichia coli and purified with Ni chromatography. The rPfPrx-1 existed as dimers under non-reducing conditions and dissociated into monomers in the presence of dithiothreitol. The PfPrx-1 protein also exists as a dimer in the parasites themselves. The reduction of the oxidized enzyme by the donation of electrons from E. coli thioredoxin (Trx)/Trx reductase system was demonstrated in its reaction with H(2)O(2), using the rPfPrx-1 protein. These results suggested that the PfPrx-1 can act as a terminal peroxidase of the parasite Trx system. An elevated expression of the PfPrx-1 protein seen in the trophozoite, the stage with active metabolism, suggests an association of the parasite Trx system with its intracellular redox control.
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PMID:Molecular characterization of a 2-Cys peroxiredoxin from the human malaria parasite Plasmodium falciparum. 1146 68

Glutathione peroxidase (GPX) reduces peroxides using reduced glutathione as the electron donor. Glutathione-dependent peroxidase activity in the soluble fraction of whole rat eye extracts (n = 3 or 4 at each stage) was the highest in the pre-natal stage (31.0 +/- 1.9 mU/mg protein) and gradually declined thereafter. The lowest value was 15.3 +/- 2.3 mU/mg protein at day 9. When the protein levels of the major selenium-containing glutathione peroxidase, GPX1, and the recently identified non-selenium-containing glutathione peroxidase, peroxiredoxin 6, were evaluated by immunoblotting using specific antibodies, they gradually declined after birth. An immunohistochemical analysis was carried out to identify the cells that express GPX1. Although the presence of GPX1 was evident only in restricted tissues, such as the corneal and lens epithelia in the adult, its levels were transiently augmented in ganglion cells, the layer of rods and cones, and pigment cells in the retina from 6 to 12 days after birth and then declined afterward. At the adult stage, the expression of GPX1 was negligible in these cells. Thus GPX1 appears to play a major role at this neonatal stage, corresponding to the period for eyelid opening. The decline in GPX1 levels after birth suggests that the detoxification of peroxides is important at this particular stage or that other, as yet unidentified peroxide-detoxifying enzymes are induced during this period.
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PMID:Transient elevation of glutathione peroxidase 1 around the time of eyelid opening in the neonatal rat. 1296 60

Patterns of expression of the 2-Cys and 1-Cys peroxiredoxin (Prx) proteins of the rodent malaria parasite Plasmodium yoelii during its life cycle were observed by immunofluorescent antibody staining and confocal laser scanning microscopy. 2-Cys Prx was expressed in the parasite cytoplasm throughout the life cycle, and the thioredoxin (Trx)-peroxidase activity of 2-Cys Prx revealed with the recombinant protein suggested that the Prx is constitutively expressed and, thus, likely plays a housekeeping role in the parasite's intracellular redox control. In contrast, 1-Cys Prx showed stage-specific expression in blood-stage parasites. The limited expression of 1-Cys Prx in the trophozoite cytoplasm suggests that 1-Cys Prx may be involved in haemoglobin metabolism by the parasite, which generates a prooxidative haem iron and increases intracellular oxidative stress. The antioxidant activity of 1-Cys Prx was tested for its ability to protect yeast enolase against inactivation of the mixed-function oxidation system. Differential expression of the two Prx proteins during the erythrocytic and insect stages suggests the importance of these proteins in protecting parasites against oxidative stress, which is generated by the parasite's metabolism and also from the environment.
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PMID:Expression profiles of peroxiredoxin proteins of the rodent malaria parasite Plasmodium yoelii. 1457 8


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