Oxoiron(IV) in Chloroperoxidase Compound II Is Basic: Implications for P450 Chemistry

• DOI: 10.1126/science.1096897
• Publication Date: 2004-06-10T19:53:06Z
• Authors: Michael T. Green; John H. Dawson; Harry B. Gray
• Keywords: Bond-dissociation energy

With the use of x-ray absorption spectroscopy, we have found that Fe-O bond in chloroperoxidase compound II (CPO-II) is much longer than expected for an oxoiron(IV) (ferryl) unit; notably, experimentally determined length 1.82(1) Å accords closely with density functional calculations on a protonated ferryl (Fe IV -OH, 1.81 Å). The basicity CPO-II [p K > 8.2 (where acid dissociation constant)] attributable to strong electron donation by axial thiolate. We suggest good model rebound intermediate P450 oxygenation cycle;with elevated p values after one-electron reduction, thiolate-ligated radicals are competent oxygenate saturated hydrocarbons at potentials can be tolerated folded polypeptide hosts.