Quantum mechanics/molecular mechanics studies on the relative reactivities of Compound I and II in cytochrome P450 enzymes

Veronica Postils, Maud Saint-Andre, Amy Timmins, Xiao-Xi Li, Yong Wong, Josep M Luis, Miquel Solà, Samuel De Visser

    Research output: Contribution to journalArticlepeer-review


    The cytochromes P450 are drug metabolizing enzymes in the body that typically react with substrates through a monoxygenation reaction. During the catalytic cycle two reduction and protonation steps generate a high-valent iron (IV)-oxo heme cation radical species called Compound I. However, with sufficient reduction equivalents present, the catalytic cycle should be able to continue to the reduced species of Compound I, called Compound II, rather than a reaction of Compound I with substrate. In particular, since electron transfer is usually on faster timescales than atom transfer, we considered this process feasible and decided to investigate the reaction computationally. In this work we present a computational study using density functional theory methods on active site model complexes alongside quantum mechanics/molecular mechanics calculations on full enzyme structures of cytochrome P450 enzymes. Specifically, we focus on the relative reactivity of Compound I and II with a model substrate for O–H bond activation. We show that generally the barrier heights for hydrogen atom abstraction are higher in energy for Compound II than Compound I for O–H bond activation. Nevertheless, for the activation of such bonds, Compound II should still be an active oxidant under enzymatic conditions. As such, our computational modelling predicts that under high-reduction environments the cytochromes P450 can react with substrates via Compound II but the rates will be much slower.
    Original languageEnglish
    JournalInternational Journal of Molecular Sciences
    Issue number7
    Early online date6 Jul 2018
    Publication statusPublished - 2018

    Research Beacons, Institutes and Platforms

    • Manchester Institute of Biotechnology


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