| Abstract
| - Density functional theory calculations are presented on the catalytic properties of a horseradish peroxidasemutant whereby the axial nitrogen atom is replaced by phosphorus. This mutant has never been studiedexperimentally and only one theoretical report on this system is known (de Visser, S. P. J. Phys. Chem. B2006, 110, 20759−20761). Thus, a one-atom substitution in horseradish peroxidase changes the properties ofthe catalytic center of the enzyme to more cytochrome P450-type qualities. In particular, the phosphorus-substituted horseradish peroxidase mutant reacts with substrates via a unique reactivity pattern, whereby alkanesare regioselectively hydroxylated even in the presence of a double bond. Reaction barriers of propeneepoxidation and hydroxylation are almost identical to ones observed for a cytochrome P450 catalyst andsignificantly higher than those obtained for a horseradish peroxidase catalyst. It is shown that the regioselectivitydifference is entropy and thermally driven and that the electron-transfer processes that occur during the reactionmechanism follow cytochrome P450-type patterns in the hydroxylation reaction.
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