Identification of Iron(III) Peroxo Species in the Active Site of the Superoxide Reductase SOR from <i>Desulfoarculus </i><i>b</i><i>aarsii</i>

Abstract

The active site of superoxide reductase SOR consists of an Fe 2+ center in an unusual [His 4 Cys 1 ] square-pyramidal geometry. It specifically reduces superoxide to produce H 2 O 2 . Here, we have reacted the SOR from Desulfoarculus baarsii directly with H 2 O 2 . We have found that its active site can transiently stabilize an Fe 3+ -peroxo species that we have spectroscopically characterized by resonance Raman. The mutation of the strictly conserved Glu47 into alanine results in a stabilization of this Fe 3+ -peroxo species, when compared to the wild-type form. These data support the hypothesis that the reaction of SOR proceeds through such a Fe 3+ -peroxo intermediate. This also suggests that Glu47 might serve to help H 2 O 2 release during the reaction with superoxide.