The non-hemehigh-spin ferric iron hydroperoxo species formed in superoxide reductase catalyzesoxidative aldehyde deformylation through its nucleophile character.This species also acts as an electrophile to catalyze oxygen atom transfer in sulfoxidation reactions, highlighting the oxidation potential of non-heme iron hydroperoxo species. The mechanisms of oxygen activation and oxidation reactions catalyzed by metalloenzymes have been thoroughly investigated during the last past decades. 1-5 For cytochrome P450 5, 6 and several non-heme iron monooxygenases, 4, 7, 8 it is now well admitted that high-valent iron-oxo species formed at their active site is the effective oxidant for organic substrate oxidation and oxygen transfer. Nevertheless, the fact that alternative species, e.g. ferric iron (hydro)peroxide intermediate, 1 or other metal-oxidant adducts, 9,