Thioredoxins are small proteins of approximately 12 kD that reduce disulfide bridges of target proteins by the reversible formation of a disulfide bridge between two neighboring Cys residues present in the active site (Try-Cys-Gly-Pro-Cys). Thioredoxins have been found to regulate a variety of biological reactions in prokaryotic and eukaryotic cells (Holmgren, 1985). In higher plants, two thior...

A search of the disulfide reductase activities expressed in the adult stage of the free-living platyhelminth Dugesia dorotocephala was carried out. Using GSSG or DTNB as substrates, it was possible to obtain a purified fraction containing both GSSG and DTNB reductase activities. Through the purification procedure, both disulfide reductase activities were obtained in the same chromatographic pea...

Numerous studies in animal models and more recent studies in humans have demonstrated cancer chemopreventive effects with Se. There is extensive evidence that monomethylated forms of Se are critical metabolites for chemopreventive effects of Se. Induction of apoptosis in transformed cells is an important chemopreventive mechanism. Apoptosis can be triggered by micromolar levels of monomethylate...

The ribonucleotide reductase system of Escherichia coli B participates in the biosynthesis of DNA by reducing ribonucleoside diphosphates to the corresponding deoxyribonucleotides. The enzyme is regulated in a complicated way by allosteric modifiers. We now find that infection of E. coli with the bacteriophage T4 results in the appearance of a new ribonucleotide reductase system which shows a s...

This reaction in vitro requires the combined function of three pure Escherichia coli proteins, namely the Bl and B2 subunits of ribonucleotide reductase and glutaredoxin. The stoichiometry was demonstrated by determinations of the products r3H]dCDP and GSSG. The standard assay couples oxidation of NADPH to the reduction of GSSG by glutathione reductase. The apparent K,,, value of glutaredoxin w...

Defense against oxidative stress in mammals includes the regeneration of the major thiol reductants glutathione and thioredoxin by glutathione reductase and thioredoxin reductase (TrxR), respectively. In contrast, Drosophila, and possibly insects in general, lacks glutathione reductase and must rely solely on the TrxR system. The mammalian TrxRs described so far are selenoproteins that utilize ...