The Catalytic Site of Glutathione Peroxidases

Tosatto, Silvio C. E.; Bosello, Valentina; Fogolari, Federico; Mauri, Pierluigi; Roveri, Antonella; Toppo, Stefano; Flohé, Leopold; Ursini, Fulvio; Maiorino, Matilde

doi:10.1089/ars.2008.2055

Cited by 158 publications

(103 citation statements)

References 50 publications

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“…Parallel lines were obtained in Lineweaver-Burk plots, indicating a ping-pong reaction mechanism (Fig. 2C), as expected for other Cys-based peroxidases (31,32). Using a bisubstrate kinetic approach (33), K m values in the micromolar range for lipoamide and t-BHP were obtained (Table 1, first lane, and supplemental Fig.…”

Section: Ohr Interacts With Lipoylated Enzymes Insupporting

confidence: 75%

Ohr (Organic Hydroperoxide Resistance Protein) Possesses a Previously Undescribed Activity, Lipoyl-dependent Peroxidase

Cussiol

Alegria

Szweda

et al. 2010

Journal of Biological Chemistry

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The Ohr (organic hydroperoxide resistance) family of 15-kDa Cys-based, thiol-dependent peroxidases is central to the bacterial response to stress induced by organic hydroperoxides but not by hydrogen peroxide. Ohr has a unique three-dimensional structure and requires dithiols, but not monothiols, to support its activity. However, the physiological reducing system of Ohr has not yet been identified. Here we show that lipoylated enzymes present in the bacterial extracts of Xylella fastidiosa interacted physically and functionally with this Cys-based peroxidase, whereas thioredoxin and glutathione systems failed to support Ohr peroxidase activity. Furthermore, we could reconstitute in vitro three lipoyl-dependent systems as the Ohr physiological reducing systems. We also showed that OsmC from Escherichia coli, an orthologue of Ohr from Xylella fastidiosa, is specifically reduced by lipoyl-dependent systems. These results represent the first description of a Cys-based peroxidase that is directly reduced by lipoylated enzymes.

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Section: Ohr Interacts With Lipoylated Enzymes Insupporting

confidence: 75%

Ohr (Organic Hydroperoxide Resistance Protein) Possesses a Previously Undescribed Activity, Lipoyl-dependent Peroxidase

Cussiol

Alegria

Szweda

et al. 2010

Journal of Biological Chemistry

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show abstract

“…These amino acid residues demonstrate strict conservation in all Sec containing GPxs, and their mutation disrupts GPx enzymatic activity (239,240). In addition, an Asn residue (Asn137, numbering is based on human GPx4) was found to be necessary for enzymatic function (346). This amino acid is located in close proximity to catalytic Sec and was proposed to form a catalytic tetrad in the active site.…”

Section: A Glutathione Peroxidasesmentioning

confidence: 99%

Selenoproteins: Molecular Pathways and Physiological Roles

Labunskyy

Hatfield

Gladyshev³

2014

Physiological Reviews

1,028

835

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Selenium is an essential micronutrient with important functions in human health and relevance to several pathophysiological conditions. The biological effects of selenium are largely mediated by selenium-containing proteins (selenoproteins) that are present in all three domains of life. Although selenoproteins represent diverse molecular pathways and biological functions, all these proteins contain at least one selenocysteine (Sec), a seleniumcontaining amino acid, and most serve oxidoreductase functions. Sec is cotranslationally inserted into nascent polypeptide chains in response to the UGA codon, whose normal function is to terminate translation. To decode UGA as Sec, organisms evolved the Sec insertion machinery that allows incorporation of this amino acid at specific UGA codons in a process requiring a cis-acting Sec insertion sequence (SECIS) element. Although the basic mechanisms of Sec synthesis and insertion into proteins in both prokaryotes and eukaryotes have been studied in great detail, the identity and functions of many selenoproteins remain largely unknown. In the last decade, there has been significant progress in characterizing selenoproteins and selenoproteomes and understanding their physiological functions. We discuss current knowledge about how these unique proteins perform their functions at the molecular level and highlight new insights into the roles that selenoproteins play in human health.

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“…From the about 30 selenoproteins present in humans (8), the enzymology of the glutathione peroxidase (GPx) family has been most extensively studied (9,10). Although all mammalian GPxs reduce hydroperoxides by means of glutathione, their individual functions seem to be different.…”

Section: Introductionmentioning

confidence: 99%

Glutathione Peroxidase 2 Inhibits Cyclooxygenase-2–Mediated Migration and Invasion of HT-29 Adenocarcinoma Cells but Supports Their Growth as Tumors in Nude Mice

et al. 2008

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The selenoprotein gastrointestinal glutathione peroxidase 2 (GPx2) is up-regulated in a variety of cancer cells with thus far unknown consequences. Therefore, two clones of a human colon cancer cell line (HT-29) in which GPx2 was stably knocked down by small interfering RNA (siRNA; siGPx2) were used to test whether cancer-relevant processes are affected by GPx2. The capacity to grow anchorage independently in soft agar was significantly reduced in siGPx2 cells when compared with controls (i.e., HT-29 cells stably transfected with a scramble siRNA). The weight of tumors derived from siGPx2 cells injected into nude mice was lower in 9 of 10 animals. In contrast, in a wound-healing assay, wound closure was around 50% in controls and 80% in siGPx2 cells, indicating an enhanced capacity of the knockdown cells to migrate. Similarly, invasion of siGPx2 cells in a Transwell assay was significantly increased. Migration and invasion of siGPx2 cells were inhibited by celecoxib, a cyclooxygenase-2 (COX-2)-specific inhibitor, but not by A-tocopherol. Selenium supplementation of cell culture medium did not influence the results obtained with siGPx2 cells, showing that none of the other selenoproteins could replace GPx2 regarding the described effects. The data show that GPx2 inhibits malignant characteristics of tumor cells, such as migration and invasion, obviously by counteracting COX-2 expression but is required for the growth of transformed intestinal cells and may, therefore, facilitate tumor cell growth. The data also shed new light on the use of selenium as a chemopreventive trace element: a beneficial effect may depend on the stage of tumor development. [Cancer Res 2008;68(23):9746-53]

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The Catalytic Site of Glutathione Peroxidases

Cited by 158 publications

References 50 publications

Ohr (Organic Hydroperoxide Resistance Protein) Possesses a Previously Undescribed Activity, Lipoyl-dependent Peroxidase

Ohr (Organic Hydroperoxide Resistance Protein) Possesses a Previously Undescribed Activity, Lipoyl-dependent Peroxidase

Selenoproteins: Molecular Pathways and Physiological Roles

Glutathione Peroxidase 2 Inhibits Cyclooxygenase-2–Mediated Migration and Invasion of HT-29 Adenocarcinoma Cells but Supports Their Growth as Tumors in Nude Mice

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