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1.
Selenium metabolism and bioavailability 总被引:13,自引:0,他引:13
Lynne A. Daniels 《Biological trace element research》1996,54(3):185-199
Selenium (Se) is at once an essential and toxic nutrient that occurs in both inorganic and organic forms. The biological functions
of Se are mediated through at least 13 selenoproteins that contain Se as selenocysteine (Se-cyst). The endogenous synthesis
of this amino acid from inorganic Se (selenide Se−2) and serine is encoded by a stop codon UGA in mRNA and involves a unique tRNA. Selenium can also substitute for sulfur in
methionine to form an analog, selenomethionine (Se-meth), which is the main form of Se found in food. Animals cannot synthesize
Se-meth or distinguish it from methionine and as a result it is nonspecifically incorporated into a wide range of Se-containing
proteins. The metabolic fate of Se varies according to the form ingested and the overall Se status of an individual. This
paper reviews the bioavailability, including absorption, transport, metabolism, storage, and excretion, of the different forms
of exogenous and endogenous Se. 相似文献
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Philip J. White 《Biochimica et Biophysica Acta (BBA)/General Subjects》2018,1862(11):2333-2342
Background
Selenium (Se) is not an essential element for plants, although it can benefit their growth and survival in some envionments. Excess tissue Se concentrations are toxic. The ability to sequester Se in vacuoles, synthesise non-toxic Se metabolites, or volatilise Se compounds determines maximum tissue Se concentrations and the ability to colonise seleniferous soils.Scope of review
This review first classifies plant species on their abilities to accumulate Se in their tissues and to colonise seleniferous soils. It then presents our knowledge of Se uptake by roots and its movement within the plant, the primary and secondary metabolism of Se in plants, effects of Se on sulfur and nitrogen metabolism, and the detoxification of excessive Se by plants. Finally, it presents a current hypothesis for the evolution of seleniferous flora.Major conclusions
Selenium and sulfur share the same primary metabolism. When grown in the same environment, most plant species have similar tissue Se/S quotients. However, Se-hyperaccumulator species, which can have tissue Se concentrations >1?mg?g?1 dry matter, have larger Se/S quotients than other species. Secondary Se metabolism determines differences in tissue Se concentration among plant species. Among non-hyperaccumulator species, alliums and brassicas have particularly large tissue Se concentrations. Selenium hyperaccumulation results from the effective metabolic detoxification of Se in tissues.General significance
Differences in Se metabolism determine the maximum Se concentrations in plant tissues, which is important for the delivery of Se to diets of herbivores and for the evolution of plant species to colonise seleniferous soils. 相似文献4.
Selenium metabolism in Escherichia coli 总被引:3,自引:0,他引:3
Escherichia coli will reduce selenite (SeO 3 2- ) andselenate (SeO 4 2- ) to elemental selenium Se 0 . Seleniumwill also become incorporated intoproteins as part of the amino acids selenocysteine or selenomethionine.The reaction of selenitewith glutathione produces selenodiglutathione (GS-Se-GS). Selenodiglutathioneand itssubsequent reduction to glutathioselenol (GS-SeH) are likely the key intermediatesin the possiblemetabolic fates of selenium. This review presents the possible pathwaysinvolving selenium in E. coli. Identification of intermediates and potentialprocesses from uptake of the toxic oxyanions through to theirdetoxification will assist us inunderstanding the complexities of metalloid oxyanion metabolism in thesebacteria. 相似文献
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Fenghua Qian Sougat Misra 《Critical reviews in biochemistry and molecular biology》2019,54(6):484-516
AbstractSelenium (Se) is an essential trace element that functions in the form of the 21st amino acid, selenocysteine (Sec) in a defined set of proteins. Se deficiency is associated with pathological conditions in humans and animals, where incorporation of Sec into selenoproteins is reduced along with their expression and catalytic activity. Supplementation of Se-deficient population with Se has shown health benefits suggesting the importance of Se in physiology. An interesting paradigm to explain, in part, the health benefits of Se stems from the observations that selenoprotein-dependent modulation of inflammation and efficient resolution of inflammation relies on mechanisms involving a group of bioactive lipid mediators, prostanoids, which orchestrate a concerted action toward maintenance and restoration of homeostatic immune responses. Such an effect involves the interaction of various immune cells with these lipid mediators where cellular redox gatekeeper functions of selenoproteins further aid in not only dampening inflammation, but also initiating an effective and active resolution process. Here we have summarized the current literature on the multifaceted roles of Se/selenoproteins in the regulation of these bioactive lipid mediators and their immunomodulatory effects. 相似文献
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Shadia E. Ramadan A. A. Razak Y. A. Yousseff N. M. Sedky 《Biological trace element research》1988,18(1):161-170
Fusarium sp. was isolated from Sinai soil at Egypt. It showed tendency to tolerate high concentrations of selenium in the form of sodium
selenite up to 3.5% (w/v). The microscopic examination revealed some morphological distortions. However, the fungus was capable
to circumvent the toxic effect of selenium. The fungus possesses strong reducing ability as high quantities of elemental selenium
were precipitated within the fungal cells as well as on the surface of the fungal hyphae and spores. The presence of selenium
increased the cellular contents of carbohydrates, proteins, and lipids. Labeling studies indicate the incorporation of selenite
into certain amino acids: selenocysteine and selenocysteic acid. Moreover, the presence of selenium induced the biosynthesis
of several types of low molecular weight proteins. The results demonstrated different modes of detoxification of selenium
toxicity. 相似文献
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Dipple Anthony Pigott Margaret A. Milner John A. 《Biological trace element research》1986,10(2):153-157
Since selenium has been found to exert a protective action against carcinogenesis in various systems, the mechanism where-by
sodium selenite inhibits DNA binding of the carcinogen, 7,12-dimethylbenz[a]anthracene, was investigated. It was found that
selenite preferentially reduced DNA binding occurring through ananti-dihydrodiol epoxide metabolite of this carcinogen by inhibiting the induction of an enzyme system that generates this specific
reactive metabolite. 相似文献
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The metabolism of selenite, selenocysteine (SeCys), and selenomethionine (SeMet) was studied in three human lymphoblast cell
lines with defects in the transsulfuration pathway and in control cells without this defect. There were very little differences
in the induction of glutathione peroxidase (GPX) activity by selenite and SeCys among these cells. However, markedly higher
levels of SeMet were required to induce GPX activity in transsulfuration defective cells than in control cells. Surprisingly,
the addition of pyridoxal phosphate (PLP) to the media resulted in elevated GPX activity in all cells regardless of the chemical
form of Se used. There is no explanation for this effect of PLP, but it is not through direct reaction with GPX or on the
alteration of sulfhydryl groups. 相似文献
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Polyamine metabolism and function 总被引:60,自引:0,他引:60
12.
Chanoine JP 《BioFactors (Oxford, England)》2003,19(3-4):137-143
Selenium is an integral component of the enzymes glutathione peroxidase (GPx) and iodothyronine deiodinases. Although selenium nutrition could conceivably affect thyroid function in infants, children and adolescents, available data suggest that the effect of selenium deficiency on thyroid function is relatively modest. In patients with isolated selenium deficiency (such as patients with phenylketonuria receiving a low-protein diet), peripheral thyroid hormone metabolism is impaired but there are no changes in thyrotropin (TSH) or clinical signs of hypothyroidism, suggesting that these patients are euthyroid. Selenium supplementation may be advisable to optimize tissue GPx activity and prevent potential oxidative stress damage. In areas where combined selenium and iodine deficiencies are present (such as endemic goiter areas in Central Africa), selenium deficiency may be responsible for the destruction of the thyroid gland in myxoedematous cretins but may also play a protective role by mitigating fetal hypothyroidism. In these areas, selenium supplementation should only be advocated at the same time or after iodine supplementation. In patients with absent or decreased production of thyroid hormones and who rely solely on deiodination of exogenous L-thyroxine for generation of the active triiodothyronine (such as patients with congenital hypothyroidism), selenium supplementation may optimize thyroid hormone feedback at the pituitary level and decrease stimulation of the residual thyroid tissue. 相似文献
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Selenium stimulates pancreatic beta-cell gene expression and enhances islet function 总被引:1,自引:0,他引:1
Campbell SC Aldibbiat A Marriott CE Landy C Ali T Ferris WF Butler CS Shaw JA Macfarlane WM 《FEBS letters》2008,582(15):2333-2337
The present study investigated the role of selenium in the regulation of pancreatic beta-cell function. Utilising the mouse beta-cell line Min6, we have shown that selenium specifically upregulates Ipf1 (insulin promoter factor 1) gene expression, activating the -2715 to -1960 section of the Ipf1 gene promoter. Selenium increased both Ipf1 and insulin mRNA levels in Min6 cells and stimulated increases in insulin content and insulin secretion in isolated primary rat islets of Langerhans. These data are the first to implicate selenium in the regulation of specific beta-cell target genes and suggest that selenium potentially promotes an overall improvement in islet function. 相似文献
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N. Seiler 《Neurochemistry international》1981,3(2):95-110
Putrescine, spermidine and spermine are simple alipathic polycations of ubiquitous occurrence. The pathways of biosynthesis and catabolism, and changes of the concentrations of these compounds in brain under various conditions are discussed.The pharmacological properties of the polyamines have not yet revealed functions which are characteristic only for the CNS, but preliminary evidence suggests structural roles in membranes and a modulatory function in certain neuronal systems. 相似文献
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The consequences of renal functional impairment on aluminum (Al) excretion are not clear inasmuch as little is known about its glomerular filtration, tubular reabsorption, or secretion. The association of Al and the etiology of the dialysis encephalopathy syndrome and osteomalacia among patients with uremia suggests that renal functional impairment is a prerequisite for increased body Al stores. However, considerable evidence argues against the concept that tissue Al accumulation occurs as a simple consequence of renal failure. Many dialysis patients have high parathyroid hormone (PTH) concentrations that have been associated with neurologic abnormalities, bone disease, and anemia. The toxicity of PTH could be either direct or indirect by influencing the metabolism of potentially toxic substances such as Al. Our studies in normal rats suggest that gastrointestinal Al absorption and specific tissue burdens are enhanced by PTH, but not irreversibly, because the withdrawal of PTH resulted in Al egress. Dialysis patients are often treated with vitamin D analogs to prevent or control consequences of hyperparathyroidism and impaired 1,25-dihydroxycholecalciferol synthesis. Although some reports suggest that high bone Al in osteomalacia may be responsible for vitamin D resistance, our studies with normal rats suggest that its metabolites may also increase tissue Al burdens independent of PTH action. Thus, several factors operative in uremia other than impaired renal function may contribute to altered Al metabolism and, consequently, to its toxicity. 相似文献
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Overview of retinoid metabolism and function 总被引:13,自引:0,他引:13