Preparation and properties of ferrous chloroperoxidase complexes with dioxygen, nitric oxide, and an alkyl isocyanide. Spectroscopic dissimilarities between the oxygenated forms of chloroperoxidase and cytochrome P-450.

Dioxygen Activation by the Biofuel-Generating Cytochrome P450 OleT

“…The ferrous enzyme, with a λ max ∼ 412 nm, rapidly decays to form a species with a Soret maximum at 426 nm and a predominant Q-band at 550 nm with a small shoulder at 580 nm. The Soret maximum is red-shifted relative to many 60,61 but not all 62 O 2bound CYPs and is well within the large range observed for comparable species in thiolate heme proteins such as chloroperoxidase (CPO) 63 and nitric oxide synthase (NOS). 64,65 The difference in absorbance features of oxyOleT versus those of many other CYPs may arise from differences at the proximal "cys-pocket" or from interactions with bound dioxygen at the distal pocket, both of which are significantly different in CYP152s.…”

On the reaction of ferric heme proteins with nitrite and sulfite

“…SiRHP, 18.1 at 590 nm (Siegel et al, 1982); NiR, 76 at 386 nm (Vega & Kamin, 1977); cytochrome cdu 312 at 407 nm (Huynh et al, 1983); Mb, 3.3 at 632 nm (Smith & Williams, 1968); HRP, 11.3 at 497 nm (Ohlsson & Paul, 1976); catalase, 8.1 at 622 nm (Kirkman et al, 1987); CPO, 13.7 at 515 nm (Sono et al, 1985); and cytochrome c, 8.4 at 550 nm (Margalit & Schejter, 1970). In the case of catalase, the extinction coefficient is expressed in units per heme, while with cytochrome cdx the units are per molecule (2 heme d per molecule).…”

“…"Sono et al (1986). •'"Sono et al (1985). loss of the high-spin signal of the resting enzyme, but instead of EPR silence an absorption-type EPR signal with gz at 2.71-2.73 was frequently seen.…”

Cytochrome P-450 and chloroperoxidase: thiolate-ligated heme enzymes. Spectroscopic determination of their active-site structures and mechanistic implications of thiolate ligation

“…In the MCD spectra (Figure 12), fewer similarities are seen between the three oxygenated proteins. 52 The spectral features of oxychloroperoxidase are consistently red-shifted from those of the other two proteins. In the Soret region, asymmetric MCD curves are seen for oxychloroperoxidase and oxy-P-450-CAM, while oxymyoglobin has symmetrical line shapes.…”

“…The rates of autoxidation of the oxygenated derivatives of P-450-CAM and chloroperoxidase (7.0 and 5.8 X 10-4 s-1, respectively) were essentially identical at -10 °C and pH 6.0.52 Surprisingly, despite the extensive similarities between the spectral properties of parallel derivatives of chloroperoxidase and P-450 discussed above, the UVvisible absorption and MCD spectra of oxychloroperoxidase and oxy-P-450-CAM are distinct from each other. 52 In particular, the Soret peak of the UV-visible absorption spectrum of oxychloroperoxidase is over 10 nm red-shifted from that of oxy-P-450-CAM, and the former has a sharp a peak at 587 nm, where only a slight shoulder is seen in that region of the spectrum of oxy-P-450-CAM. As for the red-shift of the Soret peak of oxychloroperoxidase, the oxy-P-450 model system of Budyka et al127 displayed large solvent effects on the wavelength of the Soret peak with the peak position shifting up to 10 nm to longer wavelength with increasing solvent polarity.…”