Peroxiredoxin VI (Prx VI, 1– Cys Prx) is a member of Peroxiredoxin Family, an antioxidant enzyme that detoxifies reactive oxygen species and has a cysteine at their active site. Six isoforms (Prx I to VI) of Prx exist in all eukaryotic cells. These isoforms are classified into three subgroups (2-Cys, atypical 2-Cys, and 1– Cys). Prx VI modulates various receptorsignaling pathways and protects cells from cell death induced by oxidative stress. The active site cystein (Cys47) is oxidized to cysteine sulfenic acid(Cys47-SOH) by H2O2. However, the resulting Cys47-SOH does not form a disulfide bond because of unavailability of another Cys-SH nearby. It can be reduced by nonphysiological thiols such as DDT but is not transformed by Thioredoxin/Thioredoxin Reductase or GSH. Occasionally, the sulfenic intermediate is hyperoxidized to sulfinic or sulfonic acid, resulting in inactivation of peroxidase activity.