An Overoxidation Journey with a Return Ticket

摘要

Peroxiredoxins (Prxs) are enzymes lacking prosthetic groups that catalyze the reduction of hydrogen peroxide (H_2O_2) and organic hydroperoxides (1, 2). They are ubiquitous proteins found in organisms ranging from bacteria to humans. In mammalian cells, they typically constitute 0.1 to 0.8% of the total soluble protein of the cell. At over 10~6 copies per cell, PrxII is the second most abundant protein in mouse red blood cells. The abundance of peroxiredoxins partly compensates for their moderate catalytic proficien- cy. For example, other antioxidant enzymes such as catalase and glutathione peroxidase reduce peroxide at rates that are one to three orders of magnitude greater than the peroxide reduction rate of the peroxiredoxins. In eukaryotic cells, the peroxiredoxins are both antioxidants and regulators of H_2O_2-mediated signaling. Importantly, human PrxII has been implicated in several disease states including cancer and neu-rodegenerative disorders (3, 4). Reports in this issue by Wood et al. (5) on page 650 and Woo et al. (6) on page 653 shed light on the mechanisms that enable peroxiredoxins to perform this dual role.