Moessbauer investigations of high-spin ferrous heme proteins. II. Chloroperoxidase, horseradish peroxidase, and hemoglobin

Abstract

Reduced samples of chloroperoxidase, horseradish peroxidase, and deoxyhemoglobin were studied by Mössbauer spectroscopy in strong magnetic fields. The intricate paramagnetic spectra of chloroperoxidase were evaluated in detail in the framework of a spin Hamiltonian pertinent to high-spin ferrous iron. The studies strongly suggest that, in their reduced states, chloroperoxidase from Caldariomyces fumago and cytochrome P-450 from Pseudomonas putida have similar, if not identical ligand structures of the heme iron. The spectral similarities of these two proteins, noted in an earlier Mössbauer investigation, are further explored and substantiated. Reduced horseradish peroxidase and deoxyhemoglobin, on the other hand, show high-field Mössbauer spectra that differ considerably from each other and, in particular, from those of the P-450 type, suggesting a different ligand arrangement of the heme iron for each case.