Selenium Biochemistry

Abstract

The toxicity of selenium to animals and plants has been known and extensively documented since the 1930's, but it is only during the past 15 years that selenium has also been shown to be an essential micronutrient for animals and bacteria. Very little is known about the specific role or roles of selenium and, to date, there are only three enzyme-catalyzed reactions that have been shown to require the participation of a selenium-containing protein. These are the reactions catalyzed by (i) formate dehydrogenase of bacteria, (ii) glycine reductase of clostridia, and (iii) glutathione peroxidase of erythrocytes. The common denominator of these selenium-dependent processes is that they are all oxidation-reduction reactions. A fourth selenoprotein has been isolated from skeletal muscle of sheep but its catalytic function has not been identified. The form in which selenium occurs in these selenoproteins is unknown. The selenoprotein of clostridial glycine reductase contains selenium in a covalently bound form. Studies in progress indicate that this may be an organoselenium compound not previously detected in nature. Identification of the chemical nature of selenium in proteins participating in electron transport processes should enable us to determine its specific role and to understand the basic defects in certain cardiac and skeletal muscle degenerative diseases which are selenium-deficiency syndromes. The greater availability and ease of isolation of the selenoprotein of the bacterial glycine reductase system makes this the biological material of choice for studies on the mechanism of action of selenium. An added attractive feature of this system is that it can conserve the energy made available by the reductive deamination of glycine in a biologically useful form by synthesizing ATP.

Growth of a rat neuroblastoma cell line in serum-free supplemented medium.

“…The element selenium is an essential nutrient for many different animal and bacterial species and has antioxidant properties as well (21,25,26). Brain contains low levels of selenium compared to other tissues, such as kidney or liver (27).…”

“…More extensive process formation is seen in N2 than in serum-supplemented medium, and other differentiated properties have been retained as well. 25-cm2 surface area) in 4 ml of medium in a humidified atmosphere of 5% C02/95% air at 370C and subcultured every 4-6 days with a trypsin/EDTA solution (0.1%/0.9 mM in Ca2+-and Mg2+-free phosphate-buffered saline).…”

Purification and Properties of Reduced Ferredoxin: CO2 Oxidoreductase from Clostridium pasteurianum, a Molybdenum Iron‐Sulfur‐Protein

“…The particulate enzyme from Desulfovibrio vulgaris utilizes a c-type cytochrome as the natural acceptor whereas the particulate enzyme from enterobacteriaceae and from Vibrio succinogenes appears to couple with menaquinone via a b-type cytochrome (for a recent review see [26]). The formate dehydrogenases from the various sources are different with respect to molecular weight [27 -321 and composition (molybdenum [30], tungsten [34-381, heme [30], non-heme iron and acid-labile sulfur [29,30], selenium [30,35,38,39] and flavins [29,40]). However, all formate dehydrogenases appear to have one property in common: they are inhibited by azide and other monovalent anions known to be effective ligands to transition metals suggesting that they are all metalloenzymes [26].…”

Enhancement Effect of Palladium Addition in the Determination of Selenium in Organic-Matrix Solutions by Electrically Heated Carbon Furnace Atomic Absorption Spectrometry

“…Following this finding, some animal nutritionists recognized that several important liverstock diseases, such as white muscle disease of cattle sheep, exudative diathesis of chick, liver necrosis of rats and muscular dystrophy in a variety of animals, are actually selenium deficiency syndromes. 2 Recently several selenium-containing amino acids, peptides and proteins have been isolated both from bacteria, animals and green plants. 2 Some of the proteins are enzymes such as glutathione peroxidase or glycine reductase.…”

“…2 Recently several selenium-containing amino acids, peptides and proteins have been isolated both from bacteria, animals and green plants. 2 Some of the proteins are enzymes such as glutathione peroxidase or glycine reductase.…”