Figure 1.

Role of thioredoxin system in antioxidant defense. Thioredoxin (TXN) catalyzes the reduction of disulfides (S-S) within oxidized cellular proteins, which can act to restore protein function. An important target of thioredoxin is the antioxidant peroxiredoxin (PRX), which can detoxify hydrogen peroxide. In reducing target proteins, thioredoxin becomes oxidized. In order to reactivate thioredoxin, thioredoxin reductase (TXNRD) reduces TXN using reducing equivalents obtained from NADPH. S-S = oxidized form. SH = reduced form.