NMR INVESTIGATION OF ISOTOPICALLY LABELED CYANIDE DERIVATIVES OF LIGNIN PEROXIDASE AND MANGANESE PEROXIDASE

The H-1 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 N-15 shift values of N-15-enriched CN- in the cyanide derivatives of LiP and MnP have also been measured. The shift patterns, both for N-15 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 N-15 and those of proximal histidine protons and the Fe3+/Fe2+ redox potentials.