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Issue 20, 2004
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Quantum chemical studies of dioxygen activation by mononuclear non-heme iron enzymes with the 2-His-1-carboxylate facial triad

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Abstract

Density functional theory with the B3LYP hybrid functional has been used to study the mechanisms for dioxygen activation by four families of mononuclear non-heme iron enzymes: α-ketoacid-dependent dioxygenases, tetrahydrobiopterin-dependent hydroxylases, extradiol dioxygenases, and Rieske dioxygenases. These enzymes have a common active site with a ferrous ion coordinated to two histidines and one carboxylate group (aspartate or glutamate). In contrast to the heme case, this type of weak field environment always leads to a high-spin ground state. With the exception of the Rieske dioxygenases, which have an electron source outside the active site, the dioxygen activation process passes through the formation of a bridging-peroxide species, which then undergoes O–O bond cleavage finally leading to the four electron reduction of O2. In the case of tetrahydrobiopterin- and α-ketoacid-dependent enzymes, the O–O heterolysis yields a high-valent iron–oxo species, which is capable of performing a two-electron oxidation chemistry on various organic substrates. For the other two families of enzymes (extradiol dioxygenases and Rieske dioxygenases) the substrate oxidation and the O–O bond cleavage are found to be coupled. In the extradiol dioxygenases the product of the O–O bond cleavage is a ferric iron with an oxy-substrate with a mixture of radical and anionic character, which is essential for the selectivity of the catechol cleavage.

Graphical abstract: Quantum chemical studies of dioxygen activation by mononuclear non-heme iron enzymes with the 2-His-1-carboxylate facial triad

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Publication details

The article was received on 02 Jun 2004, accepted on 05 Aug 2004 and first published on 27 Aug 2004


Article type: Perspective
DOI: 10.1039/B408340G
Citation: Dalton Trans., 2004, 3153-3162
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    Quantum chemical studies of dioxygen activation by mononuclear non-heme iron enzymes with the 2-His-1-carboxylate facial triad

    A. Bassan, T. Borowski and P. E. M. Siegbahn, Dalton Trans., 2004, 3153
    DOI: 10.1039/B408340G

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