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Thioredoxin reductase (TrXR) is a ubiquitous enzyme which reduces the thioredoxin protein by a disulfide oxidoreductase activity. This enzyme belongs to the flavoprotein family which needs cofactors to catalyze the NADPH dependent reaction. NADPH cofactor allows electrons transmission during the reaction via FAD from enzyme to oxidized protein. The thioredoxin system is thus composed of thioredoxin reductase, NADPH and thioredoxin with the following reaction:

TrxR_reaction.jpg

TrxR1 belongs to one of the two forms of mammalian TrxR enzymes mostly present in cytosol contrary to TrxR2 which is only mitochondrial. TrxR1 is heterogeneous protein which is present in most tissues and she is specific of the small thioredoxin 1 protein (Trx1). Its capacity to reduce oxidized Trx1 is important to maintain the active site of Trx1. The redox activity of Trx1 reduced is the key of its biological activity. TrxR1 can thus regulate Trx1 activities by its NADPH dependent reduction specificity.

Structure

Catalytic mechanism

Biological function

Biological functions of TrxR1 depend directly of thioredoxin activities. Trx1 can interact with many partners in different cellular compartments. Its biological function is cellular localisation dependent. Reductase activity of Trx1 can regulate cell growth or apoptosis for example but in the nucleus, Trx can bind to different transcription factors. The key role of Trx is its capacity to defense against oxidative damage.

=== A central role for oxidative stress

Diseases