X-ray Absorption Spectroscopy Comparison of the Active Site Structures of Phanerochaete chrysosporium Lignin Peroxidase Isoenzymes H2, H3, H4, H5, H8, and H10

The iron heme and its immediate environment can provide information that is pivotal to our understanding of the structural and mechanistic features that confer unusual properties to the heme peroxidases. X-ray absorption spectroscopy (XAS), which is ideally suited for the investigation of the local environment and electronic structure of the heme iron of hemeproteins, has been used to characterize a variety of lignin peroxidase and manganese-dependent peroxidase isoenzymes produced by the white rot fungus Phanerochaete chrysosporium. The data suggest no differences within the error in the first coordination shell of iron for the isoenzymes H2, H3, H4, H5, H8, and H10 examined in this study. The pyrrole nitrogens are at a distance of 2.05 ± 0.015 Å, and the proximal histidine nitrogens are at 1.93 ± 0.02 Å, while the sixth ligands are located at 2.17 ± 0.03 Å. Significant differences are observed in higher coordination shells which may be related to conformational differences in the heme.