Evidence for two ferryl species in chloroperoxidase compound II. Journal   Journal of the American Chemical Society. Citation   J Am Chem Soc. 128(18):6147-53 Publication date   2006 May 10 Authors   Stone KL Hoffart LM Behan RK Krebs C Green MT Investigators   Michael Green Carsten Krebs Abstract   Using a combination of density functional calculations and Mössbauer spectroscopy, we have examined chloroperoxidase compound II (CPO-II). The Mössbauer spectrum of CPO-II suggests the presence of two distinct ferryl species in an approximately 70:30 ratio. Density functional calculations and cryogenic reduction and annealing experiments allow us to assign the major species as an Fe(IV)OH intermediate. The Mössbauer parameters of the minor component are indicative of an authentic iron(IV)oxo species, but we have found the 70:30 ratio to be pH invariant. The unchanging ratio of component concentrations is in agreement with CPO-II's visible absorption spectrum, which shows no change over the enzyme's range of pH stability.