Catalytically self-sufficient P450 CYP102 (cytochrome P450 BM-3): Resonance Raman spectral characterization of the heme domain and of the holoenzyme

The resonance Raman spectra of CYP102 holoenzyme and of the CYP102 heme domain in the reduced state have been obtained for the first time. Spectra of the oxidized heme domain have also been measured. Whereas the spectra of the isolated heme domain are similar to those obtained for other hexacoordinated low-spin P450s, the holoenzyme spectra exhibited unexpected features. The most plausible explanation is that they reflect an electron transfer to the heme from photoreduced flavins. The results obtained for both the oxidized and reduced heme domain bring additional support to the use of CYP102 as a model for microsomal mammalian P450 enzymes, showing that the heme moiety in CYP102 has similar properties to the hemes in microsomal P450s.