Mossbauer and electron paramagnetic resonance studies of chloroperoxidase following mechanism-based inactivation with allylbenzene

Debrunner, PG, Dexter, AF, Schulz, CE, Xia, YM and Hager, LP (1996) Mossbauer and electron paramagnetic resonance studies of chloroperoxidase following mechanism-based inactivation with allylbenzene. Proceedings of the National Academy of Sciences of the United States of America, 93 23: 12791-12798. doi:10.1073/pnas.93.23.12791


Author Debrunner, PG
Dexter, AF
Schulz, CE
Xia, YM
Hager, LP
Title Mossbauer and electron paramagnetic resonance studies of chloroperoxidase following mechanism-based inactivation with allylbenzene
Journal name Proceedings of the National Academy of Sciences of the United States of America   Check publisher's open access policy
ISSN 0027-8424
Publication date 1996-11-01
Year available 1996
Sub-type Article (original research)
DOI 10.1073/pnas.93.23.12791
Open Access Status Not Open Access
Volume 93
Issue 23
Start page 12791
End page 12798
Total pages 8
Place of publication WASHINGTON
Publisher NATL ACAD SCIENCES
Language eng
Abstract We have used Mossbauer and electron paramagnetic resonance (EPR) spectroscopy to study a heme-N-alkylated derivative of chloroperoxidase (CPO) prepared by mechanism-based inactivation with allylbenzene and hydrogen peroxide. The freshly prepared inactivated enzyme (''green CPO'') displayed a nearly pure low-spin ferric EPR signal with g = 1.94, 2.15, 2.31. The Mossbauer spectrum of the same species recorded at 4.2 K showed magnetic hyperfine splittings, which could be simulated in terms of a spin Hamiltonian with a complete set of hyperfine parameters in the slow spin fluctuation limit. The EPR spectrum of green CPO was simulated using a three-term crystal field model including g-strain. The best-fit parameters implied a very strong octahedral field in which the three T-2(2) levels of the ((3)d)(5) configuration in green CPO were lowest in energy, followed by a quartet. In native CPO, the (6)A(1) states follow the T-2(2) ground state doublet. The alkene-mediated inactivation of CPO is spontaneously reversible, Warming of a sample of green CPO to 22 degrees C for increasing times before freezing revealed slow conversion of the novel EPR species to two further spin S = 1/2 ferric species. One of these species displayed g = 1.82, 2.25, 2.60 indistinguishable from native CPO, By subtracting spectral components due to native and green CPO, a third species with g = 1.86, 2.24, 2.50 could be generated. The EPR spectrum of this ''quasi-native CPO,'' which appears at intermediate times during the reactivation, was simulated using best-fit parameters similar to those used for native CPO.
Keyword N-alkylhemins
cytochrome P450
epoxidation
three-term model
electron paramagnetic resonance simulations
Endogenous Thiolate Ligation
Hemin-Catalyzed Epoxidation
N-Alkylporphyrin Complexes
Beef-Liver Catalase
Active-Site
Compound-I
Low-Spin
Enantioselective Epoxidation
Horseradish-Peroxidase
Dealkylation Reactions
Q-Index Code C1
Q-Index Status Provisional Code
Grant ID RR01811-11
F31 GM016406
Institutional Status Unknown

Document type: Journal Article
Sub-type: Article (original research)
Collection: ResearcherID Downloads - Archived
 
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