Identification of iron(III) peroxo species in the active site of the superoxide reductase SOR from Desulfoarculus baarsii

TL;DR

This study identifies and characterizes a transient Fe3+-peroxo species in the active site of superoxide reductase from Desulfoarculus baarsii, providing insights into its reaction mechanism with superoxide.

Contribution

It reports the first spectroscopic detection of an Fe3+-peroxo intermediate in SOR, revealing its stabilization and potential role in the enzyme's function.

Findings

Fe3+-peroxo species can be stabilized in SOR

Mutation of Glu47 stabilizes the Fe3+-peroxo intermediate

Data supports a reaction pathway involving Fe3+-peroxo intermediate

Abstract

The active site of superoxide reductase SOR consists of an Fe2+ center in an unusual [His4 Cys1] square-pyramidal geometry. It specifically reduces superoxide to produce H2O2. Here, we have reacted the SOR from Desulfoarculus baarsii directly with H2O2. We have found that its active site can transiently stabilize an Fe3+-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 Fe3+-peroxo species, when compared to the wild-type form. These data support the hypothesis that the reaction of SOR proceeds through such a Fe3+-peroxo intermediate. This also suggests that Glu47 might serve to help H2O2 release during the reaction with superoxide.