Sulfur K-edge X-ray absorption spectroscopy and density functional theory calculations on superoxide reductase: role of the axial thiolate in reactivity.

ABSTRACT: Superoxide reductase (SOR) is a non-heme iron enzyme that reduces superoxide to peroxide at a diffusion-controlled rate. Sulfur K-edge X-ray absorption spectroscopy (XAS) is used to investigate the ground-state electronic structure of the resting high-spin and CN- bound low-spin FeIII forms of the 1Fe SOR from Pyrococcus furiosus. A computational model with constrained imidazole rings (necessary for reproducing spin states), H-bonding interaction to the thiolate (necessary for reproducing Fe-S bond covalency of the high-spin and low-spin forms), and H-bonding to the exchangeable axial ligand (necessary to reproduce the ground state of the low-spin form) was developed and then used to investigate the enzymatic reaction mechanism. Reaction of the resting ferrous site with superoxide and prot

SUBMITTER: Dey A 

PROVIDER: S-EPMC2533108 | biostudies-literature | 2007 Oct

REPOSITORIES: biostudies-literature