Oxoiron(IV) in Chloroperoxidase Compound II Is Basic: Implications for P450 Chemistry
Abstract
With the use of x-ray absorption spectroscopy, we have found that the Fe-O bond in chloroperoxidase compound II (CPO-II) is much longer than expected for an oxoiron(IV) (ferryl) unit; notably, the experimentally determined bond length of 1.82(1) Å accords closely with density functional calculations on a protonated ferryl (Fe^(IV)-OH, 1.81 Å). The basicity of the CPO-II ferryl [pK_a > 8.2 (where K_a is the acid dissociation constant)] is attributable to strong electron donation by the axial thiolate. We suggest that the CPO-II protonated ferryl is a good model for the rebound intermediate in the P450 oxygenation cycle; with elevated pK_a values after one-electron reduction, thiolate-ligated ferryl radicals are competent to oxygenate saturated hydrocarbons at potentials that can be tolerated by folded polypeptide hosts.
Additional Information
© 2004 American Association for the Advancement of Science. 18 February 2004; Accepted 21 April 2004. We thank M. Bollinger, I. Dmochowski, J. Labinger, M. Machczynski, M. McGuirl, A. Tezcan, and J. Winkler for helpful discussions; G. George, I. Pickering, M. Latimer, B. Butler, A. Soo Hoo, S. Debeer George, D. Durkin, and other SSRL staff members for assistance with XAS measurements; and L. Hager for a CPO sample used in the initial experiments. Supported by NIH (GM26730 to J.H.D. and DK19038 to H.B.G.), NSF, and the Arnold and Mabel Beckman Foundation.Additional details
- Eprint ID
- 51798
- Resolver ID
- CaltechAUTHORS:20141114-143753781
- NIH
- GM26730
- NIH
- DK19038
- NSF
- Arnold and Mabel Beckman Foundation
- Created
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2014-11-15Created from EPrint's datestamp field
- Updated
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2021-11-10Created from EPrint's last_modified field