There is no doubt as to the important role that free radicals and reactive oxygen species play in the cell. Disturbances in intracellular redox proteins are often accompanied by common pathologies, including diabetes, myocardial infarction, neurodegeneration, bronchopulmonary diseases, cancer, etc. Numerous antioxidant enzymes are related to various redox biology systems, the thiol oxidoreductase superfamily playing a key role. The superfamily includes thioredoxin, glutaredoxin, peroxiredoxin, protein disulfide isomerase, and glutathione peroxidase families and a number of other proteins. Apart from their antioxidant function, thiol oxidoreductases are capable of recycling hydroperoxyde to produce specific disulfide bonds within and between proteins, which significantly expands their functional range. In view of this, it is a topical problem of redox biology to characterize the superfamily members biochemically and to study their functional mechanisms.