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)

Thirty-six hours after male rats were injected with 25 mumoles cadmium chloride/ml/kg of body weight they exhibited decreased plasma and testicular glutathione (GSH) peroxidase activity, testicular atrophy and necrosis, and increased testicular thiobarbituric acid-reactive products. Seven days after injection, only the plasma GSH peroxidase activity returned to normal. The decrease in testicular GSH peroxidase activity was not reversible by dialysis against buffer or by the addition of selenium as buffered selenomethionine. In vitro inhibition of testicular GSH peroxidase activity occurred at 0.3 mM cadmium. All in vivo effects were prevented by a prior injection of 25 mumoles sodium selenite/ml/kg of body weight. Testicular GSH peroxidase may be the direct or indirect target of cadmium-induced testicular damage, and this damage results in lipid peroxidation.
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PMID:Effect of cadmium chloride on the rat testicular soluble selenoenzyme, glutathione peroxidase. 17 19

The present knowledge of glutathione (GSH) peroxidase is briefly reviewed: GSH peroxidase has a molecular weight of about 85,000, consists of four apparently-identical subunits and contains four g atom of selenium/mol. The enzyme-bound selenium can undergo a substrate-induced redox change and is obviously essential for activity. In accordance with the assumption that a selenol group is reversibly oxidized during catalysis, ping-pong kinetics are observed. Limiting maximum velocities and Michaelis constants, indicating the formation of an enzyme-substrate complex, are not detectable. The enzyme is highly specific for GSH but reacts with many hydroperoxides. It can be deduced from the kinetic analysis of GSH peroxidase that in physiological conditions removal of hydroperoxide is largely independent of fluctuations in the cellular concentration of GSH. However, the system will abruptly collapse if the rate of hydroperoxide formation exceeds that of regeneration of GSH. By these considerations, the pathophysiological manifestation of disorders in GSH metabolism and pentose-phosphate shunt may be explained. With regard to its low specificity for hydroperoxides, GSH peroxidase could be involved in various metabolic events such as H2O2 removal in compartments low in catalase, hydroperoxide-mediated mutagenesis, protection of unsaturated lipids in biomembranes, prostaglandin biosynthesis, and regulation of prostacyclin formation.
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PMID:Glutathione peroxidase: fact and fiction. 38 23

Neutrophils and monocytes are the prime defenders of the body against suppurative bacterial and fungal infections. To accomplish their role in inflammation, they must respond appropriately to chemotactic signals elaborated from complement and bacteria. This response predictably results in the adherence and subsequent directed movement of the phagocytes toward the infected area where they recognize opsonized microbes. Attachment of the microbes to the membrane of the cell leads to their ingestion and subsequent demise, principally by the reduced oxygen by-product H2O2, which is generated by the neutrophils and monocytes during phagocytosis. Optimal killing requires the translocation of granule myeloperoxidase into the phagocytic vacuole containing the bacteria and a suitable halide ion. Degranulation is controlled, in part, by assembled microtubules whereas ingestion requires assembly of submembrane microfilaments. Deficiency states resulting from vitamin E results in diminished membrane-related chemotaxis and ingestion, whereas depletion of cellular GSH results in defective microtubule assembly preventing the normal increase in adherence, chemotaxis, degranulation, and microbicidal activity of the phagocytic cells. Deficiency states resulting in dysfunction of the microtubule system include neutrophil glutathione synthetase deficiency, rodent glutathione peroxidase deficiency, and the Chediak-Higashi syndrome.
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PMID:Role of membrane vitamin E and cytoplasmic glutathione in the regulation of phagocytic functions of neutrophils and monocytes. 39 94

Sulphydryl oxidase, an enzyme isolated from milk, catalyses the de novo synthesis of disulphide bonds. Thiol groups in amino acids or their derivatives, peptides, and proteins are oxidized; molecular oxygen serves as the electron acceptor and undergoes a two-electron reduction to hydrogen peroxide. Michaelis constants vary considerably amongst various substrates; glutathione is a particularly good substrate. Inhibition studies and oxidation of 1,3-diphenylisobenzofuran suggest a mechanism involving an electron transfer to singlet O2 forming an enzyme-bound hydroperoxy group. Evidence for a direct interaction of the enzyme with horseradish peroxidase was also obtained. Although protein-folding appears to be thermodynamically favoured, rates of spontaneous acquisition of functional three-dimensional structures in disulphide-containing proteins have appeared disturbingly slow. In the presence of sulphydryl oxidase, functional structure is rapidly acquired by both reductively unfolded ribonuclease A and reductively denatured immobilized chymotrypsinogen A as judged by restoration of native fluorescence characteristics and biological activity. Preliminary data suggest that unlike thiol:protein-disulphide oxidoreductase, protein-disulphide isomerase, or GSSG/GSH redox systems, sulphydryl oxidase does not permit a 'reshuffling' of disulphide bonds.
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PMID:Sulphydryl oxidase: oxidation of sulphydryl groups and the formation of three-dimensional structure in proteins. 39 63

The effect of dietary selenium and vitamin E on the important cellular antioxidant defense systems was studied in rat erythrocytes. Weanling male Sprague-Dawley rats were fed a basal selenium and vitamin E deficient diet and supplemented with either none or 0.5 ppm selenium and either none or 45 ppm vitamin E for 35 or 40 days. Depletion of dietary selenium resulted in marked decrease of glutathione (GSH) peroxidase in the red cells, but the levels of GSH, catalase and superoxide dismutase were not significantly altered. The red cells of rats fed the basal diet deficient in both selenium and vitamin E had significantly lower levels of GSH and GSH peroxidase, but not of catalase and superoxide dismutase, than in those fed the basal diet and supplemented with either selenium, vitamin E or both. The results suggest that depletion of dietary selenium and vitamin may have a precipitate effect on lowering the levels of GSH and GSH peroxidase in rat erytyrocytes.
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PMID:Effect of dietary selenium and vitamin E on the antioxiant defense systems of rat erythrocytes. 46 73

In order to find the basic defect in the Hermansky-Pudlak Syndrome (HPS), biochemical studies of platelets and leucocytes were undertaken. Glutathione levels of platelets were normal and regeneration of GSH similar to controls occurred after incubation with diamide (a specific agent for GSH oxidation). Phospholipid and fatty acid composition of HPS platelets was normal. The amount of peroxides found in platelet membranes was not elevated. A subnormal aggregation with arachidonic acid could be obtained in PRP using a high concentration of arachidonic acid (2 mM), but normal malondialdehyde levels were measured, suggesting a normal prostaglandin synthesis in HPS platelets. Glutathion peroxidase and p-phenylenediamide-mediated peroxidase (PPD-peroxidase) were normal in leucocytes of 1 HPS patient. Lysosomal enzymes as far as investigated were normal.
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PMID:Biochemical studies in Hermansky-Pudlak syndrome. 49 77

Weanling male Sprague-Dawley rats were fed either a synthetic diet supplemented with 11 mg vitamin E/kg body weight (to approximate average U.S. human dietary intake) or a commercial rat chow for 5 wk. At 2 months of age, rats were exposed to either 0.0, 0.1, or 0.2 ppm ozone continuously for 7 days. Morphological lesions were consistently present in centriacinar regions of lungs of both groups of rats at the 0.2 ppm level. At 0.1 ppm ozone, two of six rats fed the synthetic diet and two of five fed lab chow had minimal centriacinar lesions. Biochemical assays showeed that the activities of glutathione (GSH) peroxidase, GSH reductase, and G-6-P dehydrogenase and level of nonprotein sulfhydryls in the lungs of rats fed the synthetic diet and exposed to 0.1 ppm were elevated to about one-half the level that was produced by 0.2 ppm. The authors conclude that the level whereby there are no observable morphologic effects for short-term exposure to ozone in 2-month-old rats is less than, but close to, 0.1 ppm.
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PMID:Pulmonary alterations in rats exposed to 0.2 and 0.1 ppm ozone: a correlated morphological and biochemical study. 51 18

Morphological changes in response to 2-chloro-4-acetotoluidine (CAT) toxicity in the quail appeared in the form of progressive necrosis of the kidney, particularly the proximal tubular epithelial cells. Changes at 32 hr after the CAT administration included vacuolar degeneration, dilatation of distal tubules containing hyaline and granular casts, overt necrosis, and deposition of urate casts in collecting tubules. There were no striking histopathological changes in the liver at 24 hr. However, small focal necrotic lesions were seen 32 hr after the CAT administration. A 40% protection against the toxicity of CAT at the lower dose was seen in quail pretreated with phenobarbital. The protection offered by phenobarbital pretreatment was attributed to a quantitative shunting of CAT and/or its reactive metabolite along the microsomal-mediated metabolic pathway of the kidney responsible for their inactivation. Administration of reduced glutathione (GSH) to quail treated with CAT offered little protection against the toxicity. The quail treated with a toxic dose of CAT had an increased level of thiobarbituric acid (TBA) reacting products in the liver, with a concomitant decrease in GSH content. This suggests that lipid peroxidation may be involved in CAT-induced hepatic damage of quail. It was hypothesized that the depletion of protective GSH stores coincident with gradual shutdown of the protective peroxidase system of the kidney may occur in a more advanced stage of CAT toxicity in quail. This would then result in a severe disturbance in renal excretion of uric acid and in frank necrosis of renal tubules.
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PMID:Effects of 2-chloro-4-acetotoluidine (CAT) toxicity on biochemical and morphological alterations in quail. 54 4

Toxic doses of butylated hydroxytoluene (BHT), a phenolic antioxidant commonly used as a food additive, are known to produce lung damage. In this study, 3 days after a single ip injection of 62.5, 215, or 500 mg/kg BHT in mice there was a dose-dependent increase in lung weight. This concentration dependence with injected BHT was accompanied by increases in lung DNA and nonprotein sulfhydryl levels and in whole lung tissue enzyme activities of glutathione (GSH) peroxidase, GSH reductase, glucose-6-phosphate dehydrogenase, and superoxide dismutase. The increased enzyme activities are considered to correspond to inflammatory and proliferative pulmonary changes resulting from acute lung cell injury and necrosis, which have been described previously, and cannot be construed as evidence for a primary oxidant-induced pulmonary lesion. The mechanism of BHT-induced lung changes may not be related to the antioxidant property of BHT, since vitamin E, n-propyl gallate, ethoxyquin, N,N'-p-phenylenediamine, and the structurally similar compound, butylated hydroxyanisole did not appear to produce the gross anatomical or biochemical lung changes observed with BHT.
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PMID:Effect of butylated hydroxytoluene and other antioxidants on mouse lung metabolism. 59 82

The formation of glutathione radicals, the evolution of nascent oxygen or the peroxidatic reaction with catalase complex I are considered as possible mechanisms for the oxidation of mercury vapor by red blood cells. To select among these, the uptake of atomic mercury by erythrocytes from different species was studied and related to their various activities of catalase (hydrogenperoxide : hydrogen-peroxide oxidoreductase, EC 1.11.1.6) and glutathione peroxidase (glutathione : hydrogen-peroxide oxidoreductase, EC 1.11.1.9). A slow and continuous infusion of diluted H2O2 was used to maintain steady concentrations of complex I. 1% red cell supsensions were found most suitable showing high rates of Hg uptake and yielding still enough cells for subsequent determinations. The results indicate that the oxidation of mercury depends upon the H2O2-generation rate and upon the specific acticity of red-cell catalase. The oxidation occurred in a range of the catalase-H2O2 reaction where the evolution of oxygen could be excluded. Compounds reacting with complex I were shown to be effective inhibitors of the mercury uptake. GSH-peroxidase did not participate in the oxidation but rather, was found to inhibit it by competing with catalase for hydrogen peroxide. These findings support the view that elemental mercury is oxidized in erythrocytes by a peroxidatic reaction with complex I only.
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PMID:Enzymatic oxidation of mercury vapor by erythrocytes. 65 39


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