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Issue 6, 2009
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myo-Inositol oxygenase: a radical new pathway for O2 and C–H activation at a nonheme diiron cluster

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Abstract

The enzyme myo-inositol oxygenase (MIOX) catalyzes conversion of myo-inositol (cyclohexan-1,2,3,5/4,6-hexa-ol or MI) to D-glucuronate (DG), initiating the only known pathway in humans for catabolism of the carbon skeleton of cell-signaling inositol (poly)phosphates and phosphoinositides. Recent kinetic, spectroscopic and crystallographic studies have shown that the enzyme activates its substrates, MI and O2, at a carboxylate-bridged nonheme diiron(II/III) cluster, making it the first of many known nonheme diiron oxygenases to employ the mixed-valent form of its cofactor. Evidence suggests that: (1) the Fe(III) site coordinates MI via its C1 and C6 hydroxyl groups; (2) the Fe(II) site reversibly coordinates O2 to produce a superoxo-diiron(III/III) intermediate; and (3) the pendant oxygen atom of the superoxide ligand abstracts hydrogen from C1 to initiate the unique C–C-bond-cleaving, four-electron oxidation reaction. This review recounts the studies leading to the recognition of the novel cofactor requirement and catalytic mechanism of MIOX and forecasts how remaining gaps in our understanding might be filled by additional experiments.

Graphical abstract: myo-Inositol oxygenase: a radical new pathway for O2 and C–H activation at a nonheme diiron cluster

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Article information


Submitted
25 Jul 2008
Accepted
29 Sep 2008
First published
26 Nov 2008

Dalton Trans., 2009, 905-914
Article type
Perspective

myo-Inositol oxygenase: a radical new pathway for O2 and C–H activation at a nonheme diiron cluster

J. M. Bollinger, Y. Diao, M. L. Matthews, G. Xing and C. Krebs, Dalton Trans., 2009, 905
DOI: 10.1039/B811885J

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