Proton NMR investigation into the basis for the relatively high redox potential of lignin peroxidase

Lignin peroxidase shares several structural features with the well-studied horseradish peroxidase and cytochrome c peroxidase but carries a higher redox potential. Here the heme domain of lignin peroxidase and the lignin peroxidase cyanide adduct was examined by ¹H NMR spectroscopy, including nuclear Overhauser effect and two-dimensional measurements, and the findings were compared with those for horseradish peroxidase and cytochrome c peroxidase. Structural information was obtained on the orientation of the heme vinyl and propionate groups and the proximal and distal histidines. The shifts of the el proton of the proximal histidine were found to be empirically related to the Fe³⁺/Fe²⁺ redox potentials.