2006
DOI: 10.1021/bi0526276
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Oxygen Activation by a Mixed-Valent, Diiron(II/III) Cluster in the Glycol Cleavage Reaction Catalyzed by myo-Inositol Oxygenase

Abstract: myo-Inositol oxygenase (MIOX) catalyzes the ring-cleaving, four-electron oxidation of its cyclohexan-(1,2,3,4,5,6-hexa)-ol substrate (myo-inositol, MI) to d-glucuronate (DG). The preceding paper [Xing, G., Hoffart, L. M., Diao, Y., Prabhu, K. S., Arner, R. J., Reddy, C. C., Krebs, C., and Bollinger, J. M., Jr. (2006) Biochemistry 45, 5393−5401] demonstrates by Mössbauer and electron paramagnetic resonance (EPR) spectroscopies that MIOX can contain a non-heme dinuclear iron cluster, which, in its mixed-valent (… Show more

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Cited by 54 publications
(93 citation statements)
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“…With the exception of MIOX, all dinuclear nonheme-iron oxygenases and oxidases studied to date use the fully reduced forms of their cofactors to activate O 2 (32)(33)(34)(35)(36)(37)(38), and the mixedvalent Fe II /Fe III forms are usually only marginally stable in these enzymes (28,39,40). By contrast, MIOX employs the mixedvalent form of its diiron cluster to promote substrate and O 2 activation and accordingly stabilizes this state, allowing its accumulation in 60-70% yield (17 (Fig. 4).…”
Section: Resultsmentioning
confidence: 99%
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“…With the exception of MIOX, all dinuclear nonheme-iron oxygenases and oxidases studied to date use the fully reduced forms of their cofactors to activate O 2 (32)(33)(34)(35)(36)(37)(38), and the mixedvalent Fe II /Fe III forms are usually only marginally stable in these enzymes (28,39,40). By contrast, MIOX employs the mixedvalent form of its diiron cluster to promote substrate and O 2 activation and accordingly stabilizes this state, allowing its accumulation in 60-70% yield (17 (Fig. 4).…”
Section: Resultsmentioning
confidence: 99%
“…More definitive proof that the Fe II /Fe III state is the active enzyme form was sought by FQ EPR experiments testing for a rapid, cyclic reaction of O 2 with the Fe II /Fe III cofactor in the substrate-bound complex, an observation crucial in establishing that the mixed-valent state is the catalytically active cofactor form in MIOX (17). Because oxidation of (R)-OH-AEP to glycine and phosphate is charge balanced with the four-electron reduction of O 2 (Fig.…”
Section: Resultsmentioning
confidence: 99%
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“…It was recently shown, using EPR and Mössbauer spectroscopy, that MIOX is a new member of the nonheme diiron-dependent dioxygen-activating family (6). Interestingly, the sequence indicated strong dissimilarity to other members of this family (6) that all feature a core four-helix bundle, as shown by the structures of, for example, protein R2 of ribonucleotide reductase (7), soluble methane monoxygenase (8), and stearoylacyl carrier protein ⌬ 9 -desaturase (9, 10).…”
mentioning
confidence: 99%
“…Interestingly, the sequence indicated strong dissimilarity to other members of this family (6) that all feature a core four-helix bundle, as shown by the structures of, for example, protein R2 of ribonucleotide reductase (7), soluble methane monoxygenase (8), and stearoylacyl carrier protein ⌬ 9 -desaturase (9, 10). Furthermore, MIOX uses an antiferromagnetically coupled high spin mixed valent diiron (II/III) cluster for catalysis, and the mixed valent state is regenerated after each cycle of catalysis (6).…”
mentioning
confidence: 99%