NMR Investigation of Isotopically Labeled Cyanide Derivatives of Lignin Peroxidase and Manganese Peroxidase

The ¹H NMR spectroscopy was used to study lignin peroxidase (LiP) and manganese peroxidase (MnP) containing deuterated histidines. LiP and MnP were obtained from a histidine auxotroph of the fungus Phanerochaete chrysosporium grown in the presence of deuterated histidines. The derivatives with deuterated histidines have allowed a firm assignment of the protons of the distal and proximal histidines. We have also found that the LiP from this strain exhibits different orientations of the 2-vinyl group compared to the LiP from the strain previously studied. Mobility of the group has also been detected, thus explaining the apparent inconsistency between X-ray solid-state and NMR solution data. The ¹⁵N shift values of ¹⁵N-enriched CN⁻ in the cyanide derivatives of LiP and MnP have also been measured. The shift patterns, both for ¹⁵N and for the proximal histidine protons of several peroxidases, are consistent with predominant contact shift contributions which reflect the bond strength of the metal-axial ligand. Finally, our results confirm a correlation between shift values of ¹⁵N and those of proximal histidine protons and the Fe³⁺/Fe²⁺ redox potentials.