Principal Active Species of Horseradish Peroxidase, Compound I: A Hybrid Quantum Mechanical/Molecular Mechanical Study
- 13 September 2005
- journal article
- Published by American Chemical Society (ACS) in Journal of the American Chemical Society
- Vol. 127 (39), 13611-13621
- https://doi.org/10.1021/ja0534046
Abstract
The active species, Compound I, of horseradish peroxidase (HRP) has been investigated by quantum mechanical/molecular mechanical (QM/MM) calculations using 10 different QM regions. In accord with experimental data, the lowest doublet and quartet states are found to be virtually degenerate, with two unpaired electrons on the FeO moiety and one localized on the porphyrin in an a2u-dominant orbital with a minor, but nonnegligible, a1u component. The proximal ligand appears to be imidazole rather than imidazolate. The hydrogen-bonding network around the FeO moiety (i.e., Arg38 and His42) has significant influence on the axial bonds and the spin density distribution in the FeO moiety. Including this network in the QM region was found to be essential for reproducing the experimental Mössbauer parameters. The protein environment shapes most of the subtle features of Compound I of HRP.Keywords
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