Synergistic effect of thioredoxin and its reductase from Kluyveromyces marxianus on enhanced tolerance to multiple lignocellulose-derived inhibitors.

BACKGROUND: Multiple lignocellulose-derived inhibitors represent great challenges for bioethanol production from lignocellulosic materials. These inhibitors that are related to the levels of intracellular reactive oxidative species (ROS) make oxidoreductases a potential target for an enhanced tolerance in yeasts. RESULTS: In this study, the thioredoxin and its reductase from Kluyveromyces marxianus Y179 was identified, which was subsequently achieved over-expression in Saccharomyces cerevisiae 280. In spite of the negative effects by expression of thioredoxin gene (KmTRX), the thioredoxin reductase (KmTrxR) helped to enhance tolerance to multiple lignocellulose-derived inhibitors, such as formic acid and acetic acid. In particular, compared with each gene expression, the double over-expression of KmTRX2 and KmTrxR achieved a better ethanol fermentative profiles under a mixture of formic acid, acetic acid, and furfural (FAF) with a shorter lag period. At last, the mechanism that improves the tolerance depended on a normal level of intracellular ROS for cell survival under stress. CONCLUSIONS: The synergistic effect of KmTrxR and KmTRX2 provided the potential possibility for ethanol production from lignocellulosic materials, and give a general insight into the possible toxicity mechanisms for further theoretical research.

The thioredoxin system--from science to clinic.

The thioredoxin system-formed by thioredoxin reductase and its characteristic substrate thioredoxin-is an important constituent of the intracellular redox milieu. Interactions with many different metabolic pathways such as DNA-synthesis, selenium metabolism, and the antioxidative network as well as significant species differences render this system an attractive target for chemotherapeutic approaches in many fields of medicine-ranging from infectious diseases to cancer therapy. In this review we will present and evaluate the preclinical and clinical results available today. Current trends in drug development are emphasized.

Arabidopsis thaliana NAPHP thioredoxin reductase. cDNA characterization and expression of the recombinant protein in Escherichia coli.

Using a clone characterized in the course of a random sequencing programme of Arabidopsis thaliana, two cDNAs encoding plant type cytosolic NADPH-dependent thioredoxin reductase (NTR) have been isolated. Their sequence homology with Escherichia coli NRT (the only thioredoxin reductase of known primary structure) is about 45%. In addition, analysis of the sequence of the encoded polypeptide (333 amino acids) reveals that several motifs are conserved in the FAD, central and NADPH binding domains, suggesting a similar folding of the protein. Definitive proof that the clone ATTHIREDB indeed encodes NTR was obtained by expressing the recombinant protein in E. coli cells. It was observed that plant type NTR was strongly overproduced (about 10 mg homogeneous protein could be purified per liter of culture). The recombinant enzyme is homodimeric, each subunit containing an FAD prosthetic group. Recombinant plant type NTR is as effective as E. coli NTR in the DTNB (5,5'-dithiobis nitrobenzoic acid) reduction reaction, but its affinity for thioredoxin substrates was strikingly different. These results are discussed in relation to the primary structures of NADPH thioredoxin reductases.