Evidence for compound I formation in the reaction of cytochrome P450cam with m-chloroperbenzoic acid.

During the reaction of m-chloroperbenzoate with low spin ferric form of cytochrome P450cam, the formation of at least four transient intermediates was detected by employing rapid scan absorption spectrometry. Among them, the first one which appeared within 10 msec after the start of reaction gave an absorption spectrum indistinguishable from that of compound I of chloroperoxidase, another thiolate-heme protein. The intermediate exhibited the major absorption maxima at 367 and 694 nm, while chloroperoxidase compound I is known to have the maxima at 367 and 688 nm. The shapes of the bands at 367 nm were very similar to each other. Based on these spectral similarities, we suggest that the intermediate found in this study is the compound I of cytochrome P450cam.