The P-450 Nature of the Carbon Monoxide Complex of Ferrous Chloroperoxidase

The absorption spectrum of the carbon monoxide complex of ferrous chloroperoxidase from Caldariomyces fumago has been shown to be quite similar to the characteristic spectrum of CO complexes of cytochromes of the P-450 type. Comparison of other spectral properties of chloroperoxidase and cytochrome P-450cam reveals a striking resemblance between the two proteins. The Soret absorption maxima for native, reduced, cyanide, nitrous oxide, and N-phenylimidazole complexes are quite similar. N-Phenylimidazole, a potent inhibitor of the cytochrome P-450cam-catalyzed hydroxylation of camphor, is a very effective inhibitor of a chloroperoxidase-catalyzed peroxidation reaction. Like P-450, chloroperoxidase undergoes characteristic spectral changes in the presence of substrates and nitrogenous compounds. Type I and type II spectral changes have been observed. Carefully controlled denaturation of chloroperoxidase resulted in the formation of a species having a spectrum essentially identical with that of cytochrome P-420, the denatured form of P-450. The spectral similarities described here indicate that both proteins provide quite similar environments for the heme prosthetic group. Both proteins also compare favorably with respect to physical properties such as molecular weight, high content of acidic amino acids, and low isoelectric point.