Ferrous Porphyrin-Mercaptide Complexes. Models for Reduced Cytochrome P-450
Chang, C.K. and David Dolphin
J. Am. Chem. Soc.
Interactions of mercaptide ion and Fe(II) porphyrins under various conditions were studied. The normally weak chelating ability of mercaptide towards Fe(II) porphyrins was substantially enhanced by converting it to crown ether complexes. When exposed to CO and O2 the Fe(II)-mercaptide/crown ether complexes formed new spectral species which bore the same optical properties, in the Soret and visible regions, as the CO adduct of reduced cytochrome P 450. It is conjectured that the 5th coordinating site of the heme Fe in cytochrome P 450 is a mercaptide anion of unusual coordinating power, possibly a deprotonated cysteine residue.