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

Human peroxiredoxin 3 ( Hs Prx3) 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 Hs Prx3 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 × 10 7 M -1 s -1 ) and hyperoxidation (~2 × 10 7 M -1 s -1 ). The endoperoxide-hydroperoxide PGG 2 , an intermediate in prostanoid synthesis, oxidized Hs Prx3 with a similar rate constant, but was less effective in causing hyperoxidation. Biophysical methodologies suggest that Hs Prx3 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 Hs Prx3 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 Hs Prx3 hyperoxidation, a modification that has been detected in vivo under physiological and pathological conditions.