Optical and Electron Paramagnetic Resonance Studies on the Model for Cytochrome P-450

Abstract

The model system, which showed previously the hydroxylations to aniline and p-toluidine, consisting of hemin, cysteine and pyridine exhibited very similar absorption and EPR spectra to cytochrome P-450 at 293 and 77°K. From the spectral properties the axial cysteinate S-Fe-N (pyridine) coordination is necessary to show a low-spin state of porphyrin at 293°K. In the presence of trace amount of pyridine, a transition of the high-spin state observed at 293°K to the low-spin state of porphyrin was detected at 77°K.