Raman-assisted crystallography reveals end-on peroxide intermediates in a nonheme iron enzyme

TL;DR

This study used Raman-assisted crystallography to identify and characterize end-on peroxide intermediates in a nonheme iron enzyme, providing insights into its reaction mechanism involving transient hydrogen bonds.

Contribution

The paper reports the first direct observation of end-on iron-(hydro)peroxo intermediates in superoxide reductase crystals using combined X-ray and Raman spectroscopy.

Findings

Identified iron-(hydro)peroxo intermediates at 1.95 Å resolution.

Demonstrated end-on binding mode of peroxide in the enzyme.

Revealed role of hydrogen bond networks in peroxide cleavage.

Abstract

Iron-peroxide intermediates are central in the reaction cycle of many iron-containing biomolecules. We trapped iron(III)-(hydro)peroxo species in crystals of superoxide reductase (SOR), a nonheme mononuclear iron enzyme that scavenges superoxide radicals. X-ray diffraction data at 1.95 angstrom resolution and Raman spectra recorded in crystallo revealed iron-(hydro)peroxo intermediates with the (hydro)peroxo group bound end-on. The dynamic SOR active site promotes the formation of transient hydrogen bond networks, which presumably assist the cleavage of the iron-oxygen bond in order to release the reaction product, hydrogen peroxide.