Thioredoxin reductase 1

Thioredoxin reductase catalyzes the reduction of the oxidized form of thioredoxin by NADPH (36). 

Thelander (131) has proposed the following structure for thioredoxin reductase  

Each subunit of the enzyme functions in a series of oxidation-reduction reactions as outlined below (130)  

The normal catalytic process involves the sequence I- -II- -III- -IV- -I, while the steps IV- V- -VI- -III may also be part of the overall reaction. Thelander (131) has pointed out that the reaction mechanism of thioredoxin reductase differs from those of glutathione reductase and lipoyldehydrogenase because during the anaerobic titration of thioredoxin reductase no flavin semiquinone intermediate could be detected. Although thioredoxin reductase contains two subunits only one octapeptide 

Thus thioredoxin reductase, like its substrate thioredoxin, contains only two amino acid residues between the two half cystine residues and in both proteins the disulfide defines a small loop of only 14 atoms. 

ATP levels and oxygen consumption [66]. Et3PAuCl treatment also reduced the potential difference across the inner mitochondrial membrane releasing sequestered calcium from mitochondria [66]. 

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Nordberg J et ai Mammalian thioredoxin reductase is irreversibly inhibited by dinitrohaiobenzenes by alkylation of both the redox active selenocysteine and its neighboring cysteine residue.) Biol Chem 1998 273 10835. 

PiaRigobello, M., Messori, L., Marcon, G., Cinellu, M.A., Bragadin, M., Folda, A., Scutari, G. and Bindoli, A. (2004) Gold complexes inhibit mitochondrial thioredoxin reductase consequences on mitochondrial functions. Journal of Inorganic Biochemistry, 98, 1634—1641. 

Bacteria, fungi, and plants have a thioredoxin reductase system involving Se-containing thioredoxin reductase (EC 1.8.1.9), NADPH, and thioredoxin. Effecting the intercellular redox poise, this system interacts in selenium... 

Deoxynucleotides for DNA synthesis are made at the nucleoside diphosphate level and then have to be phosphorylated up to the triphosphate using a kinase and ATP. The reducing equivalents for the reaction come from a small protein, thioredoxin, that contains an active site with two cysteine residues. Upon reduction of the ribose to the 2 -deoxyri-bose, the thioredoxin is oxidized to the disulfide. The thioredoxin(SS) made during the reaction is recycled by reduction with NADPH by the enzyme thioredoxin reductase. 

Mammalian thioredoxin reductases are a family of selenium-containing pyridine nucleotide-disulfide oxidoreductases. These enzymes catalyze NADPH-dependent reduction of the redox protein thioredoxin (Trx), which contains a redox-active disulfide and dithiol group and by itself may function as an efficient cytosolic antioxidant [77]. One of the functions of Trx/ thioredoxin reductase system is the NADPH-catalyzed reduction of protein disulfide [78] ... 

Mammalian thioredoxin reductase is able to reduce many substances in addition to thioredoxin such as insulin, vitamin K, alloxan, and others, while Escherichia coli enzyme is a... 

In 1986, the antioxidant effects of thioredoxin reductase were studied by Schallreuter et al. [81]. It has been shown that thioredoxin reductase was contained in the plasma membrane surface of human keratinocytes where it provided skin protection against free radical mediated damage. Later on, the reductive activity of Trx/thioredoxin reductase system has been shown for the reduction of ascorbyl radical to ascorbate [82], the redox regulation of NFkB factor [83], and in the regulation of nitric oxide-nitric oxide synthase activities [84,85],... 

Mammalian Thioredoxin Reductase Implications for the Antitumor Effects of Selenium. J. Biol. Chem. 2002, 277, 9701-9706. 

Glutathione peroxidase 6 Thioredoxin reductase 1 Thioredoxin reductase 2 Thioredoxin reductase 3... 

Glutathione peroxide was the first selenium-containing mammalian enzyme identified over 35 years ago," the same year that the selenoprotein A was identified in C. sticklandtL With the advent of the human genome sequence we now know that there are 25 selenoproteins encoded in humans, " with similar numbers encoded by other mammals. Some of the best-studied selenoproteins include five isoenzymes of thioredoxin reductase, three... 

Staples CR, Gaymard E, Stritt-Etter A-L, et al. 1998. Role of the 6484] cluster in mediating disulfide reduction in spinach ferredoxin thioredoxin reductase. Biochemistry 37 4612-20. 

Selenium Organ meats, seafood, muscle meats, cereals and grains Component of glutathione peroxidase lodothyronine deiodinase, thioredoxin reductase... 

The deoxyribonucleotides, except for deoxythymidine nucleotide, are formed from the ribonucleotides by the action of an enzyme complex, which comprises two enzymes, ribonucleoside diphosphate reductase and thioredoxin reductase (Figure 20.11). The removal of a hydroxyl group in the ribose part of the molecule is a reduction reaction, which requires NADPH. This is generated in the pentose phosphate pathway. (Note, this pathway is important in proliferating cells not only for generation... 

Thioredoxin reductase Thymidylate synthase Origin binding protein DNA poiymerases DNA heiicase... 

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