Recycling of ascorbic acid from its oxidized forms is required to maintain intracellular stores of the vitamin in most cells. Since the ubiquitous selenoenzyme thioredoxin reductase can recycle dehydroascorbic acid to ascorbate, we investigated the possibility that the enzyme can also reduce the one-electron-oxidized ascorbyl free radical to ascorbate. Purified rat liver thioredoxin reductase c...

Thioredoxin reductase (EC l&4.5), which catalyzes the reduction of the disulfide bridge in thioredoxin by NADPH, was purified from calf liver and thymus. Preparation methods, involving chromatography on DEAE-cellulose, TEAEcellulose, and Sephadex G-200 or G-100 were used to purify the calf liver enzyme llOO-fold and the thymus enzyme 2800fold. The enzyme was shown to catalyze an NADPH-dependent...

An albumin fraction extracted from wheat flour contains thioredoxin reductase (Mr = 65,000) and a heat-stable thioredoxin (Mr = 15,000) which are separated on DEAE cellulose and further purified by gel filtration. W heat thioredoxin stimulates E. coli ribonucleotide reductase but not chloroplast fructose-bis-phosphatase. The enzyme is NADPH-dependent (Km = 3.2 X 10 -6 m) . In presence of the th...

Thioredoxin reductase (EC 1.6.4.5) is a widely distributed flavoprotein that catalyzes the NADPH-dependent reduction of thioredoxin. Thioredoxin plays several key roles in maintaining the redox environment of the cell. Like all members of the enzyme family that includes lipoamide dehydrogenase, glutathione reductase and mercuric reductase, thioredoxin reductase contains a redox active disulfide...

Recent publications make it evident that the thioredoxin± thioredoxin reductase system has come of age. The four minireviews presented here attempt to put this field in perspective. The system was first recognized in the early 1960s as the reductant of methionine sulfoxide and PAPS (3 0-phosphoadenosine-5 0-phosphosulfate) in yeast and of ribonucleotides in Escherichia coli [1±3]. It became cle...

Thioredoxins (TRXs) are protein oxidoreductases that control the structure and function of cellular proteins by cleavage of a disulphide bond between the side chains of two cysteine residues. Oxidized thioredoxins are reactivated by thioredoxin reductases (TR) and a TR-dependent reduction of TRXs is called a thioredoxin system. Thiol-based redox regulation is an especially important mechanism t...

Stimulation of target gene transcription by human p53 is inhibited in budding yeast lacking the TRR1 gene encoding thioredoxin reductase. LexA/p53 fusion proteins were used to study the basis for thioredoxin reductase dependence. A fusion protein containing all 393 of the residues of p53 efficiently and specifically stimulated transcription of a LexOP-LacZ reporter gene in wild-type yeast but w...

Ribonucleotide reductases (EC 1 .I 7.4.1 and EC 1.17.4.2) catalyse the reduction of ribonucleoside 5’-diphosphates or triphosphates to the corresponding 2’-deoxyribonucleotides and are key enzymes for the onset of DNA replication during the cell cycle (Reichard, 1968; Follmann, 1974). The reduction of the 2’-hydroxyl group of the ribose moiety in a ribonucleotide is dependent on NADPH, but this...

Stimulation of target gene transcription by human p53 is inhibited in budding yeast lacking the TRR1 gene encoding thioredoxin reductase. LexA/p53 fusion proteins were used to study the basis for thioredoxin reductase dependence. A fusion protein containing all 393 of the residues of p53 efficiently and specifically stimulated transcription of a LexOPLacZ reporter gene in wild-type yeast but wa...