Enzyme glutathione peroxidase

Thí nghiệm được thực hiện trên 16 con bò đực giống Brahman (4-5 năm tuổi, khối lượng cơ thể trung bình 877,8 ± 24,15 kg) được chia thành 4 lô để nghiên cứu ảnh hưởng của mức bổ sung kẽm và selen đến chất lượng tinh dịch. Các bò đực giống được chia làm 4 nhóm trong khẩu phần ăn có hàm lượng Zn và Se với 4 mức: 100% NRC (Mức I), 105% NRC (Mức II), 110% NRC (Mức III) và không bổ sung (đối chứng).

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Previously, we demonstrated apoptotic cell death in the chorion laeve trophoblast layer of human fetal membrane tissues during the late stages of pregnancy, the progression of apoptosis during incubation in vitro, and its suppression by a low concentration of glucocorticoid hormones.

8p system191 01-06-2013 33 5   Download

This study investigated the enzymatic function of two putative plant GPXs, GPXle1 from Lycopersicon esculentum and GPXha2 from Helianthus annuus, which show sequence identities with the mammalian phospholipid hydroperoxide glutathione peroxidase (PHGPX). Both purified recombinant proteins expressed in Escherichia coli show PHGPX activity by reducing alkyl, fatty acid and phospholipid hydroperoxides but not hydrogen peroxide in the presence of glutathione.

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As an essential element, selenium is present in enzymes from several families, including glutathione peroxidases, and is thought to exert anticarcinogenic properties. A remarkable feature of selenium consists of its ability to oxidize thiols under reducing conditions. Thus, one mode of action recently suggested is the oxidation of thiol groups of metal-lothionein, thereby providing zinc for essential reactions.

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Monolayer primary cultures of thyroid cells produce, in the presence of insulin, a cytosolic inhibitor of thyroid peroxi-dase (TPO), lacto peroxidase (LPO), horseradishperoxidase (HRPO) and glutathione peroxidase (GPX). The inhibitor, localized in the cytosol, is thermostable and hydrophylic. Itsmolecularmass is less than2 kDa.The inhibitoryactivity, resistant to proteolytic and nucleolytic enzymes, disappears with sodium metaperiodate treatment, as an oxidant of carbohydrates, supporting its oligosaccharide structure....

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A 6A,6A¢-dicyclohexylamine-6B,6B¢-diselenide-bis-b-cyclodextrin (6-CySeCD) was designed and synthesized to imitate the antioxidant enzyme glutathione peroxidase (GPX). In this novel GPX model,b-cyclodextrin provided a hydrophobic environment for substrate binding within its cavity, and a cyclohexylamine group was incorporated into cyclodextrin in proximity to the catalytic selenium in order to increase the stability of the nucleophilic intermediate selenolate.

9p galaxyss3 21-03-2013 47 4   Download

A highly active glutathioneS-transferase was purified from adult German cockroaches,Blattella germanica. The purified enzyme appeared as a single band of 24 kDa by SDS⁄PAGE, and had a different electrophoretic mobil-ity than, a previously identified Sigma class glutathione S-transferase (Bla g 5).

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Glutathione peroxidases (GPXs, EC 1.11.1.9) were first discovered in mam-mals as key enzymes involved in scavenging of activated oxygen species (AOS). Their efficient antioxidant activity depends on the presence of the rare amino-acid residue selenocysteine (SeCys) at the catalytic site.

18p galaxyss3 19-03-2013 43 5   Download

The enzymatic activities of purified horseradish peroxidase, selenium-depen-dent glutathione peroxidase, thyroid peroxidase and myeloperoxidase, but not that of lactoperoxidase, were markedly enhanced when added into a reaction mixture containing 5lmnative seminal vesicle protein 4, a major protein secreted from rat seminal vesicle epithelium.

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Pycnogenol  , which is extracted from the bark of French maritime pine, has been shown to have antioxidant and free radical scavenging activities. Thioredoxin reductase (TrxR), glutathione peroxidase (GPx) and glutathi-one reductase (GR) are three central redox enzymes that are active in endogenous defence against oxidative stress in the cell.

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The production of H2O2 by isolated mitochondria is frequently used as a measure of mitochondrial superoxide formation. Matrix superoxide dismu-tase quantitatively converts matrix superoxide to H2O2. However, matrix enzymes such as the glutathione peroxidases can consume H2O2 and com-pete with efflux of H2O2 , causing an underestimation of superoxide produc-tion.

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Men catalase được tập trung nhiều trong peroxisome của tế bào và xúc tác phản ứng biến hydro peroxid thành nước và oxy. Hydroperoxyd H2O2cũng là một chất có hoạt tính cao nên độc hại. Hệ enzym catalase và glutathion peroxydase (GSHPX) có thể loại trừ nó: H2O2 catalase 2H2O + 3O2 Catalase vận chuyển H2O2 thành 2 chất hoàn toàn vô hại là nước và oxy tam bội. Nhưng catalase chỉ thể hiện tác dụng xúc tác khi nồng độ H2O2 lớn hơn 10-8 mol/l. Dưới nồng độ đó, catalase không có tác dụng. (3) Men glutathion peroxidase...

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Selenium Selenium, in the form of selenocysteine, is a component of the enzyme glutathione peroxidase, which serves to protect proteins, cell membranes, lipids, and nucleic acids from oxidant molecules. As such, selenium is being actively studied as a chemopreventive agent against certain cancers, such as prostate. Selenocysteine is also found in the deiodinase enzymes, which mediate the deiodination of thyroxine to triiodothyronine (Chap. 335).

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