Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UNIPROT:P36969 (phospholipid hydroperoxide glutathione peroxidase)
 344 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A novel glutathione peroxidase, which is active toward hydroperoxides of phospholipid in the presence of a detergent, has been purified to homogeneity from a rat liver postmicrosomal supernatant fraction by ammonium sulfate fractionation and three different column chromatographies. From a DE52 column, glutathione peroxidase active toward phosphatidylcholine dilinoleoyl hydroperoxides was eluted in one major and two minor peaks. The enzyme in the major peak was found to be separated from the "classic" glutathione peroxidase and glutathione S-transferases and further purified by Sephacryl S-200 and Mono Q column chromatographies. The purified enzyme was found to be homogeneous on polyacrylamide gel electrophoresis under nondenaturing conditions as well as that in the presence of sodium dodecyl sulfate. The molecular weight of the enzyme as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis was 22,000, and that by gel filtration was comparable, indicating that the enzyme protein is a single polypeptide. The purified enzyme was found to catalyze the reduction of phosphatidylcholine dilinoleoyl hydroperoxides to the corresponding hydroxy derivatives. The isoelectric point of the enzyme was found at pH 6.2, and the optimum pH for the enzyme activity was 8.0. The enzyme was active toward cumene hydroperoxide, H2O2, and 1-monolinolein hydroperoxides in the absence of a detergent. The enzyme activity toward phospholipid hydroperoxides was minute in the absence of a detergent but was remarkably enhanced by the addition of a detergent. From these results, the presently purified enzyme is obviously different from the classic glutathione peroxidase and also from phospholipid hydroperoxide glutathione peroxidase purified from pig heart (Ursini, F., Maiorino, M., and Gregolin, C. (1985) Biochim. Biophys. Acta 839, 62-70), though considerably similar to the latter.
 ...
PMID:Purification and characterization of a novel monomeric glutathione peroxidase from rat liver. 319 7

The reduction of membrane-bound hydroperoxides is a major factor acting against lipid peroxidation in living systems. This paper presents the characterization of the previously described 'peroxidation-inhibiting protein' as a 'phospholipid hydroperoxide glutathione peroxidase'. The enzyme is a monomer of 23 kDa (SDS-polyacrylamide gel electrophoresis). It contains one gatom Se/22 000 g protein. Se is in the selenol form, as indicated by the inactivation experiments in the presence of iodoacetate under reducing conditions. The glutathione peroxidase activity is essentially the same on different phospholipids enzymatically hydroperoxidized by the use of soybean lipoxidase (EC 1.13.11.12) in the presence of deoxycholate. The kinetic data are compatible with a tert-uni ping-pong mechanism, as in the case of the 'classical' glutathione peroxidase (EC 1.11.1.9). The second-order rate constants (K1) for the reaction of the enzyme with the hydroperoxide substrates indicate that, while H2O2 is reduced faster by the glutathione peroxidase, linoleic acid hydroperoxide is reduced faster by the present enzyme. Moreover, the phospholipid hydroperoxides are reduced only by the latter. The dramatic stimulation exerted by Triton X-100 on the reduction of the phospholipid hydroperoxides suggests that this enzyme has an 'interfacial' character. The similarity of amino acid composition, Se content and kinetic mechanism, relative to the difference in substrate specificity, indicates that the two enzymes 'classical' glutathione peroxidase and phospholipid hydroperoxide glutathione peroxidase are in some way related. The latter is apparently specialized for lipophylic, interfacial substrates.
 ...
PMID:The selenoenzyme phospholipid hydroperoxide glutathione peroxidase. 397 21

Our previous studies have implicated the selenium metabolite selenodiglutathione (SDG) in the growth inhibitory effects of selenite in vitro. Other work has suggested that reactive oxygen species, the superoxide anion and hydrogen peroxide, may be implicated in selenite toxicity. In this study the mechanism of growth inhibition by SDG and H2O2 has been compared in a mammary cell line, C57. Both SDG and H2O2 had a rapid effect on C57 cells and markedly reduced cloning efficiency within 1 h. However, the mechanisms involved seem to be different, as judged by the following observations: (i) An SDG-resistant cell line (B19) derived from C57 cells is cross-resistant to selenite, but not H2O2; (ii) SDG reduces the levels of the mRNAs for phospholipid hydroperoxide glutathione peroxidase and cytosolic glutathione peroxidase, whereas H2O2 has no effect; (iii) SDG induces both 560 kb and 50 kb DNA fragments, whereas H2O2 only induces 560 kb DNA fragments. This is of interest, since formation of high molecular weight DNA fragments has been recognized as a characteristic of apoptosis.
 ...
PMID:The selenium metabolite selenodiglutathione induces cell death by a mechanism distinct from H2O2 toxicity. 761 92

We report a transient adaptation to the oxidative stress of hydrogen peroxide (H2O2) exposure in several mammalian cell lines: Chinese hamster ovary fibroblast (CHO) cells, HA-1 cells (a defined CHO subclone), C3H 10T1/2 cells (embryonic mouse fibroblasts), V79 cells (Chinese hamster lung fibroblasts), and Clone 9 liver cells (rat liver epithelial cells). Up to 40-fold adaptive increases in resistance to H2O2 challenge occurred following pretreatment with relatively low H2O2 "priming" doses, from as little as 1.9% cell viability for untreated cells to as much as 76.5% viability for H2O2 pretreated cells. Detailed studies with HA-1 cells revealed the following pattern of responses to H2O2: very low H2O2 concentrations of 0.1 to 0.5 mumol/10(7) cells (3 to 15 microM) stimulated cell growth by 25 to 45%; low H2O2 concentrations of 2-5 mumol/10(7) cells (120 to 150 microM) induced a temporary growth-arrest, a lengthening of cell cycle from 18 h to approximately 26 h, and marked adaptive increases in H2O2 resistance; intermediate H2O2 concentrations of 9 to 14 mumol/10(7) cells (250 to 400 microM) caused permanent growth-arrest (i.e., permanent loss of replicative or divisional competence) with no evidence of necrosis; high H2O2 concentrations of 30 mumol/10(7) cells or greater (> or = 1 mM) caused an apoptotic-like necrotic cell death and destruction. The adaptive response to low H2O2 concentrations of 2-5 mumol/10(7) (120 to 150 microM) was maximal 18 h after pretreatment of HA-1 cells, declined thereafter toward baseline sensitivity, and was observed with both 7-day fix and stain procedures and clonogenic viability assays. Transient adaptation following H2O2 pretreatment of 4.15 mumol/10(7) (150 microM) involved the de novo synthesis of at least 20 proteins and was blocked by the translation inhibitor, cycloheximide. During the 18-h adaptation in HA-1 cells proteins were synthesized in three phases; early (0-4 h), middle (4-8 h), and late (8-15 h). No H2O2 response proteins were synthesized beyond 18 h after pretreatment, by which time adaptation had already maximized. Selective translational inhibition of the early, middle, or late proteins revealed that all three sets were necessary for a maximal adaptive increase in H2O2 resistance. Northern blot and enzyme activity analyses revealed no significant increases in transcription or translation of the classical antioxidant enzymes catalase, glutathione peroxidase, phospholipid hydroperoxide glutathione peroxidase, Cu, Zn superoxide dismutase, or Mn superoxide dismutase in H2O2-adapted HA-1 cells.(ABSTRACT TRUNCATED AT 400 WORDS)
 ...
PMID:Transient adaptation of oxidative stress in mammalian cells. 772 66

We hypothesize that the differential susceptibility to photic injury among different strains of rat retinas may depend on the levels of phospholipid hydroperoxide glutathione peroxidase (PHGPX) activity, one of the endogenous antioxidant enzymes in the retina. The retinas of four inbred strains of albino rat (Fischer, Wistar, Buffalo and Lewis) were analyzed for glutathione peroxidase activity using H2O2, cumene hydroperoxide, and phospholipid hydroperoxide as assay substrates. In all four strains of rat, PHGPX was observed only in the high salt extract of the retina, while peroxidases determined by H2O2 or cumene hydroperoxide were observed mainly in the low salt extract. PHGPX was highest (66.7 mU/mg) in the most light-resistant Fischer strain and lowest in the most light-sensitive Lewis strain (31.9 mU/mg), while the activity levels in the moderately light-sensitive Buffalo and Wistar strains were 46.6 and 38.5 mU/mg, respectively. In contrast, there was no significant difference in peroxidases determined by H2O2 or cumene hydroperoxide among the four strains. These observations suggested that, in rat retina, the membrane-associated PHGPX may have an important role in the defense against light-induced free radical damage.
 ...
PMID:Correlation of phospholipid hydroperoxide glutathione peroxidase activity to the sensitivity of rat retinas to photic injury. 813 90

We studied enzyme kinetics parameters of plasma glutathione peroxidase (GSHPx-P) and the major cellular enzyme, GSHPx-1, for the substrates, H2O2, linoleic acid hydroperoxide (LinOOH), and glutathione (GSH). The major objectives were to determine whether the relatively slow GSHPx-P enzyme had a lower reactivity with hydroperoxides or with GSH and to identify favored hydroperoxide substrates. The rate constants describing the reactivity of human GSHPx-P and human GSHPx-1 with LinOOH and H2O2 are in the same range; GSHPx-P is more reactive with LinOOH and GSHPx-1 is more reactive with H2O2. GSHPx-P also has a low level of reducing activity toward cholesterol 7 alpha-OOH and no detectable activity with the 5 alpha-OOH isomer in contrast to phospholipid hydroperoxide glutathione peroxidase (PHGPx) which readily reduced both isomers. GSHPx-P catalytic activity toward phospholipid hydroperoxides is demonstrable in the absence of detergents, enhanced at low concentrations by deoxycholate, and strongly inhibited by Triton X-100 and incorporation into liposomes. These properties are the opposite of PHGPx. These results suggest that GSHPx-P largely lacks the membrane interfacial properties of PHGPx. GSHPx-P exhibits a smaller GSH rate constant than GSHPx-1. This property partially explains the slower turnover of GSHPx-P with several hydroperoxide substrates; the low reactivity with GSH is not consistent with efficient GSHPx function in the bulk plasma volume. GSHPx-P kinetic properties suggest that it would function best as a free fatty acid hydroperoxidase in GSH-rich microenvironments. Minimally, the secretion of reduced enzyme would permit it to scavenge free fatty acid hydroperoxides.
 ...
PMID:Reactivity of plasma glutathione peroxidase with hydroperoxide substrates and glutathione. 823 61

Murine leukemia L1210 cells grown for 2-3 weeks in the presence of 1% serum without selenium supplementation [L.Se(-) cells] typically exhibited < 10% of the glutathione peroxidase (GPX) and phospholipid hydroperoxide glutathione peroxidase (PHGPX) activity of selenium-satisfied controls [L.Se(+) cells]. Concomitant with diminished GPX and PHGPX activity was a 1.5- to 2.0-fold increase in catalase (CAT) activity, which reverted to control levels when L.Se(-) cells were given sufficient Se for full expression of selenoperoxidase activity. Selenium manipulation affected total glutathione content similarly, but had no effect on glutathione-S-transferase or superoxide dismutase activity. Long-term growth under Se-deficient conditions resulted in a progressive additional increase in CAT activity, which maximized after ca. 5 months. These cells [referred to as L'.Se(-)] attained CAT activity levels at least 100-times greater than those of Se-supplemented [L'.Se(+)] controls, whereas their glutathione content remained elevated by approximately 70%. Supplying L'.Se(-) cells with Se resulted in a rapid elevation to full GPX activity; however, CAT failed to decline in this case, suggesting that a selection for stable CAT hyperexpressing variants had been accomplished. Quantitative immunoblot analysis indicated that the high CAT activity of L'.Se(-) cells is accounted for by an elevated level of enzyme protein. Induction of CAT and selection for CAT-rich phenotypes, as apparent for Se-starved L1210 cells, was not observed in human K562 counterparts, which lack GPX and express only a low level of PHGPX. L.Se(-) cells were found to be more sensitive to H2O2-induced killing than L.Se(+) controls, whereas L'.Se(-) cells were exceedingly more resistant to H2O2 than L'.Se(+) counterparts. By contrast, L.Se(-) and L'.Se(-) cells were both more sensitive to t-butyl hydroperoxide than Se(+) controls, consistent with CAT being unimportant in the detoxification of this peroxide compared with GPX. This appears to be the first reported evidence for CAT hyperexpression in response to selenium deprivation.
 ...
PMID:Hyperexpression of catalase in selenium-deprived murine L1210 cells. 834 49

We have characterized a new selenium-dependent glutathione peroxidase, GSHPx-GI, by expressing a GSHPx-GI cDNA isolated from human hepatoma HepG2 cells in human mammary carcinoma MCF-7 cells, which have virtually undetectable expression of either the classical cellular enzyme, GSHPx-1, or GSHPx-GI at the protein level. One of the G418-resistant clones, neo-D1, expresses the transfected GSHPx-GI cDNA. This is based on 1) the presence of an additional GSHPx-GI DNA restriction fragment detected by Southern analysis; 2) the presence of a 1.9-kilobase (kb) GSHPx-GI mRNA in addition to the 1.0-kb endogenous mRNA by Northern analysis; and 3) the appearance of a 22-kDa 75Se-labeled protein which is absent in parental MCF-7 cells revealed by SDS-polyacrylamide gel electrophoresis. GSHPx-GI expressed in neo-D1 is a tetrameric protein localized in cytosol. GSHPx-GI does not cross-react with antisera against human GSHPx-1 or human plasma glutathione peroxidase (GSHPx-P). Similar substrate specificities are found for GSHPx-1 and GSHPx-GI; they both catalyze the reduction of H2O2, tert-butyl hydroperoxide, cumene hydroperoxide, and linoleic acid hydroperoxide with glutathione, but not of phosphatidylcholine hydroperoxide. GSHPx-GI mRNA was readily detected in human liver and colon, and occasionally in human breast samples, but not other human tissues including kidney, heart, lung, placenta, or uterus. In rodent tissues, GSHPx-GI mRNA is only detected in the gastrointestinal tract, and not in other tissues including liver. In fact, GSHPx-GI appears to be the major glutathione-dependent peroxidase activity in rodent GI tract. This finding suggests that GSHPx-GI could play a major role in protecting mammals from the toxicity of ingested lipid hydroperoxides. In conclusion, we have demonstrated that GSHPx-GI is the fourth member in the selenium-dependent glutathione peroxidase family, in addition to GSHPx-1, GSHPx-P, and phospholipid hydroperoxide glutathione peroxidase (PHGPX).
 ...
PMID:Expression, characterization, and tissue distribution of a new cellular selenium-dependent glutathione peroxidase, GSHPx-GI. 842 33

The 100000Xg supernatant parasite platyhelminth Schistosoma mansoni exhibits a glutathione peroxidase activity with the substrate phosphatidylcholine hydroperoxide. Purification yielded a protein of 20 kDa molecular mass both on gel filtration column chromatography and SDS/PAGE, thus suggesting that S. mansoni expresses a protein similar to the mammalian selenoenzynic phospholipid-hydroperoxide glutathione peroxidase. Kinetic analysis and substrate specificity corroborated this assumption, the second-order rate constants for the oxidation of the ground-state enzyme (k+1) being higher with phosphatidylcholine hydroperoxide than with other peroxide substrates, such as cumene liydroperoxide or H2O2, and quantitatively similar to those of mammalian phospholipid-hydroperoxide glutathione peroxidase. Partial sequencing of the protein and selenium measurement by neutron activation analysis established that the purified peroxidase corresponded to the product of the S. mansoni gene previously reported and supposed to encode a selenium-containing glutathione peroxidase [Roche, C., Williams, D. L., Khalife, J., LePresle, T., Capron, A. & Pierce, R. J. (1994) Cloning and characterization of gene encoding Schistosoma mansoni glutathione peroxidase, Gene 138, 149 - 152]. S. mansoni thus contains a scienoperoxidase sharing molecular mass, catalytic efficiency and substrate specificity with phospholipid-hydroperoxide glutathione peroxidase, dismantling the concept that those enzymes are unique to vertebrate organisms.
 ...
PMID:A selenium-containing phospholipid-hydroperoxide glutathione peroxidase in Schistosoma mansoni. 870 88

Commercially available calf serum did not supply the cultured murine fibroblast cell line L929 with amounts of selenium and alpha-tocopherol sufficient to protect against peroxide damage. Supplementation of the culture medium with 30 microM alpha-tocopherol or 50 nM sodium selenite led to a substantial increase of cellular alpha-tocopherol concentrations from 18 +/- 3.0 to 3179 +/- 93.0 pmol/10(6) cells or cellular selenium concentrations from 0.17 +/- 0.02 to 1.75 +/- 0.16 ng/10(6) cells, respectively. L929 fibroblasts grown in selenite-containing medium also had markedly raised activities of both cytosolic glutathione peroxidase (from 11 +/- 0.9 to 67.2 +/- 4.2 mU/10(7) cells) and phospholipid hydroperoxide glutathione peroxidase (from 0.2 to 9.5 +/- 0.9 mU/10(7)cells). Supplementation with alpha-tocopherol inhibited single-strand breaks induced by low concentrations of H2O2 only, whereas an adequate selenium supply almost completely inhibited single-strand breaks induced by up to 30 microM H2O2 and also significantly reduced H2O2-induced cell death. An inadequate selenium supply and corresponding increase of GPx activity upon selenite supplementation was also observed with other cell lines, for instance, D10N, ECV-304, HepG2, and THP-1. Our data strengthen the relevance of standardized and adequate supplementation of tissue culture media with antioxidants to improve viability and genetic stability of cultured cells in general and in particular, if they are oxidatively challenged.
 ...
PMID:Conventional cell culture media do not adequately supply cells with antioxidants and thus facilitate peroxide-induced genotoxicity. 885 40


1 2 3 Next >>