Mitochondrial Peroxiredoxin 3 Is Rapidly Oxidized and Hyperoxidized by Fatty Acid Hydroperoxides

Human peroxiredoxin 3 (HsPrx3) is a thiol-based peroxidase responsible for the reduction of most hydrogen peroxide and peroxynitrite formed in mitochondria. Mitochondrial disfunction can lead to membrane lipoperoxidation, resulting in the formation of lipid-bound fatty acid hydroperoxides ((L)FA-OOHs) which can be released to become free fatty acid hydroperoxides ((f)FA-OOHs). Herein, we report that HsPrx3 is oxidized and hyperoxidized by (f)FA-OOHs including those derived from arachidonic acid and eicosapentaenoic acid peroxidation at position 15 with remarkably high rate constants of oxidation (>3.5 x 10(7) M(-1)s(-1)) and hyperoxidation (similar to 2 x 10(7) M(-1)s(-1)). The endoperoxide-hydroperoxide PGG(2), an intermediate in prostanoid synthesis, oxidized HsPrx3 with a similar rate constant, but was less effective in causing hyperoxidation. Biophysical methodologies suggest that HsPrx3 can bind hydrophobic structures. Indeed, molecular dynamic simulations allowed the identification of a hydrophobic patch near the enzyme active site that can allocate the hydroperoxide group of (f)FA-OOHs in close proximity to the thiolate in the peroxidatic cysteine. Simulations performed using available and herein reported kinetic data indicate that HsPrx3 should be considered a main target for mitochondrial (f)FA-OOHs. Finally, kinetic simulation analysis support that mitochondrial (f)FA-OOHs formation fluxes in the range of nM/s are expected to contribute to HsPrx3 hyperoxidation, a modification that has been detected in vivo under physiological and pathological conditions.