Human Thioredoxin 1 Recombinant Protein. Thioredoxins (Trx) are small, multi-functional proteins with oxidoreductaseactivity and are ubiquitous in essentially all living cells. Trx contains aredox-active disulfide/dithiol group within the conserved Cys-Gly-Pro-Cysactive site. The two cysteine residues in the conserved active centers can be oxidized to form intramolecular disulfide bonds. Reduction of the active site disulfide in oxidized Trx is catalyzed by Trx reductase with NADPH as the electron donor. The reduced Trx is a hydrogen donor for ribonucleotide reductase, the essential enzyme for DNA synthesis, and apotent general protein disulfide reductase with numerous functions in growth and redox regulations. Specific protein disulfide ta