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Journal ArticleDOI

Glutathione peroxidase activity and chemical forms of selenium in tissues of rats given selenite or selenomethionine.

01 May 1988-Journal of Inorganic Biochemistry (Elsevier)-Vol. 33, Iss: 1, pp 31-46
TL;DR: The results indicate that the form of Se administered will influence the form in the tissues, the percentage of Se with GPx and the body burden of Se.
About: This article is published in Journal of Inorganic Biochemistry.The article was published on 1988-05-01. It has received 59 citations till now. The article focuses on the topics: Selenium.
Citations
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Book ChapterDOI
15 Dec 1986

1,017 citations


Cites background from "Glutathione peroxidase activity and..."

  • ...5 mg/kg) for 8 weeks prior to mating had normal fetal development (Bergman et al., 1990)....

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Journal ArticleDOI
TL;DR: Even though SeMCYS was shown to be the most effective seleno-compound in the reduction of mammary tumours, it may not be the best choice for reduction of colon tumours because several mechanisms have been proposed on the mechanism whereby Se reduces tumours.
Abstract: Selenomethionine (Semet) is the major seleno-compound in cereal grains and enriched yeast whereas Se-methylselenocysteine (SeMCYS) is the major seleno-compound in Se-accumulator plants and some plants of economic importance such as garlic and broccoli exposed to excess Se. Animals can metabolize both Semet and SeMCYS. Epidemiological studies have indicated an inverse relationship between Se intake and the incidence of certain cancers. Blood or plasma levels of Se are usually lower in patients with cancer than those without this disorder, but inconsistent results have been found with toenail-Se values and the incidence of cancer. There have been eight trials with human subjects conducted on the influence of Se on cancer incidence or biomarkers, and except for one, all have shown a positive benefit of Se on cancer reduction or biomarkers of this disorder. This is consistent with about 100 small-animal studies where Se has been shown to reduce the incidence of tumours in most of these trials. Se-enriched yeast is the major form of Se used in trials with human subjects. In the mammary-tumour model, SeMCYS has been shown to be the most effective seleno-compound identified so far in reduction of tumours. Several mechanisms have been proposed on the mechanism whereby Se reduces tumours. Even though SeMCYS was shown to be the most effective seleno-compound in the reduction of mammary tumours, it may not be the most effective seleno-compound for reduction of colon tumours.

578 citations


Cites background from "Glutathione peroxidase activity and..."

  • ...When rats are injected with selenite, the majority of the Se is present in tissues as selenocysteine (Olson & Palmer, 1976; Beilstein & Whanger, 1988)....

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  • ...%) of the Se is present as selenocysteine (Beilstein & Whanger, 1986, 1988)....

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Journal ArticleDOI
TL;DR: There are several selenocompounds in tissues of plants and animals, and selenocysteine, the predominant selenoamino acid in tissues when inorganic selenium is given to animals, is one of them.
Abstract: There are several selenocompounds in tissues of plants and animals. Selenate is the major inorganic selenocompound found in both animal and plant tissues. Selenocysteine is the predominant selenoamino acid in tissues when inorganic selenium is given to animals. Selenomethionine is the major selenocompound found initially in animals given this selenoamino acid, but is converted with time afterwards to selenocysteine. Selenomethionine is the major selenocompound in cereal grains, grassland legumes and soybeans. Selenomethionine can also be the major selenocompound in selenium enriched yeast, but the amount can vary markedly depending upon the growth conditions. Se-methylselenocysteine is the major selenocompound in selenium enriched plants such as garlic, onions, broccoli florets and sprouts, and wild leeks.

470 citations


Cites background from "Glutathione peroxidase activity and..."

  • ...Rats injected with selenite 6–10(5) 64–70 20–34 [56–58] Rats injected with SEM (1 day) 63 22 15 [57,58] (5–35 days) 14–25 46–57 18–40 [57,58] 17 Fish 15–36 [61] 20 Vegetables 1–50 [38] Wheat Grain 12–19(6) 56–83 4–12 1–4 4–26 [39,40] Wheat Straw 97(7) 3 [39] Corn 61–64 15–16 20–24 [41] Rice 1–3 5–13 68–81 6–10 19–31 [41] Soybeans 80 [42] Grassland Legume 51–70 19–39(8) 10–13 [43] Phytoplankton(9) (15%) 1....

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  • ...One day after injection of selenomethionine, there is about three times as much selenomethionine as selenocysteine in tissues, but five or more days afterwards, the majority (46% to 57%) of the selenium is present as selenocysteine [57,58]....

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Journal ArticleDOI
TL;DR: It is concluded that dietary selenium compounds should be considered prodrugs, whose biological activity will depend on the activity of the various metabolic pathways in, and the redox status of, cells and tissues.
Abstract: The biological activity of selenium is dependent upon its speciation We aim to integrate selenium speciation and metabolism into a discussion of the mechanisms by which selenium exerts its biological activity First, we present the current status of selenium in the prevention of cancer, cardiovascular and neurodegenerative diseases with particular attention paid to the results of major chemoprevention trials involving selenium supplementation A comprehensive review of the current understanding of the metabolism of common dietary selenium compounds – selenite, selenomethionine, methylselenocysteine and selenocystine – is presented, with discussion of the evidence for the various metabolic pathways and their products The antioxidant, prooxidant and other mechanisms of the dietary selenium compounds have been linked to their disease prevention and treatment properties The evidence for these various mechanisms – in vitro, in cells and in vivo – is evaluated with emphasis on the selenium metabolites involved We conclude that dietary selenium compounds should be considered prodrugs, whose biological activity will depend on the activity of the various metabolic pathways in, and the redox status of, cells and tissues These factors should be considered in future laboratory research and in selecting selenium compounds for trials of disease prevention and treatment by selenium supplementation

442 citations

BookDOI
01 Jan 1989
TL;DR: This book contains one-half of the oral or poster presentations which were selected before the meeting was held on the basis of a one page abstract and is the reader who will have to decide whether this time consuming policy of quality assessment was warranted or not.
Abstract: In July, 1988, more than 300 scientists from 29 different countries gathered at Tiibingen, W. Germany, in order to spend 4 days discussing their favourite trace element, selenium. This meeting continued the good tradition of three previous meetings held in Corvallis/Oregon, 1976, in Lubbock/Texas, 1980, and in Beijing/China, in 1984. Incidentally, the University of Tiibingen provided a unique historical background for a Symposium devoted to recent advances in biochemistry, pharmacology, human nutrition and human health; here, the first independent depart ment of Physiological Chemistry in Germany was founded in 1845. Pro fessor H9Ppe-Seyler elucidated here the hemin structure and his student Friedrich Miescher discovered the nucleic acids. This book contains one-half of the oral or poster presentations which were selected before the meeting was held on the basis of a one page abstract. It is the reader who will have to decide whether this time consuming policy of quality assessment was warranted or not."

394 citations

References
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Journal ArticleDOI
TL;DR: Glutathione peroxidase activity is found to be associated with a relatively stable, nondialyzable, heat-labile, intracellular component which is separable from hemoglobin, by gel filtration and ammonium sulfate precipitation.

10,439 citations

Journal ArticleDOI
TL;DR: It was concluded that the reduced form of glutathione peroxidase contains the selenocysteine selenol (-SeH) at the catalytic site.
Abstract: A procedure was developed to isolate 75Se-labeled rat liver glutathione peroxidase (glutathione:H2O2 oxidoreductase, EC 1.11.1.9) at 30--50% purity with 20--30% yields in 4--5 days. Using these preparations of glutathione peroxidase, the selenium moiety in the enzyme was identified as selenocysteine by derivatizing the seleno group with either iodoacetate or ethylenimine in the intact protein, hydrolyzing the protein with 6 N HCl, and cochromatographing the 75Se-labeled products with known standards. Techniques employed were anion-exchange chromatography, cation-exchange chromatography, gel-permeation chromatography, two-dimensional thin-layer chromatography, and automated amino acid analysis. The selenocysteine moiety was identified as the catalytic site in glutathione peroxidase by specifically labeling the enzyme with [14C]iodoacetate on the 75Se-labeled selenium atom and fractionating the 14C, 75Se-labeled derivative after acid hydrolysis. It was concluded that the reduced form of glutathione peroxidase contains the selenocysteine selenol (-SeH) at the catalytic site.

441 citations

Journal ArticleDOI
TL;DR: Plasma GSHPx, like the erythrocyte enzyme, was found to contain approximately four atoms of selenium per mole of protein and is a glycoprotein, and radioimmunoassay showed that less than 0.13% of the antigenically detectable protein is found in the purified GSHpx from plasma.

399 citations

Journal ArticleDOI
TL;DR: Selenocysteine is much more reactive with halo acid derivatives than is cysteine, and reacts readily with iodoacetate even at pH values much below the pK of the selenohydryl group.

298 citations

Journal ArticleDOI
TL;DR: In this article, the results suggest the presence of selenocysteic acid in significant amounts in wheat gluten, seeds and straw from plants grown on soil to which 75Se-selenate had been added.

217 citations