Evidence for C-H cleavage by an iron-superoxide complex in the glycol cleavage reaction catalyzed by myo-inositol oxygenase.
Proc Natl Acad Sci U S A
; 103(16): 6130-5, 2006 Apr 18.
Article
en En
| MEDLINE
| ID: mdl-16606846
ABSTRACT
myo-Inositol oxygenase (MIOX) activates O2 at a mixed-valent nonheme diiron(II/III) cluster to effect oxidation of its cyclohexan-(1,2,3,4,5,6-hexa)-ol substrate [myo-inositol (MI)] by four electrons to d-glucuronate. Abstraction of hydrogen from C1 by a formally (superoxo)diiron(III/III) intermediate was previously proposed. Use of deuterium-labeled substrate, 1,2,3,4,5,6-[2H]6-MI (D6-MI), has now permitted initial characterization of the C-H-cleaving intermediate. The MIOX.1,2,3,4,5,6-[2H]6-MI complex reacts rapidly and reversibly with O2 to form an intermediate, G, with a g = (2.05, 1.98, 1.90) EPR signal. The rhombic g-tensor and observed hyperfine coupling to 57Fe are rationalized in terms of a (superoxo)diiron(III/III) structure with coordination of the superoxide to a single iron. G decays to H, the intermediate previously detected in the reaction with unlabeled substrate. This step is associated with a kinetic isotope effect of > or =5, showing that the superoxide-level complex does indeed cleave a C-H(D) bond of MI.
Texto completo:
1
Colección:
01-internacional
Base de datos:
MEDLINE
Asunto principal:
Espectroscopía de Resonancia por Spin del Electrón
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Superóxidos
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Inositol-Oxigenasa
Límite:
Animals
Idioma:
En
Revista:
Proc Natl Acad Sci U S A
Año:
2006
Tipo del documento:
Article
País de afiliación:
Estados Unidos
Pais de publicación:
EEUU
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ESTADOS UNIDOS
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ESTADOS UNIDOS DA AMERICA
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EUA
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UNITED STATES
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UNITED STATES OF AMERICA
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US
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USA