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Caracterización del intermediario areno-oxidante en ToMOH como una especie de diirón (III)

Leslie J Murray¹, Sunil G Naik, Danilo O Ortillo

¹Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.

Journal of the American Chemical Society

|October 31, 2007

Resumen

Los investigadores identificaron un intermediario clave de diironio (III) en el tolueno/o-xileno monooxigenasa. Este intermedio actúa como el oxidante activo, facilitando la hidroxilación del sustrato y revelando información sobre los mecanismos de activación del dioxígeno.

Área de la Ciencia:

La bioquímica es la bioquímica.
Enzimología Enzimología.
Química de las metaloproteínas.

Sus antecedentes:

La tolueno/o-xileno monooxigenasa (TOXM) es crucial para la degradación de los hidrocarburos aromáticos.
Comprender el mecanismo de TOXM, particularmente su activación por oxígeno, es vital para la biorremediación y el biocatálisis.
Estudios anteriores han implicado a los centros de hierro en el ciclo catalítico de TOXM.

Objetivo del estudio:

Para caracterizar el intermedio diironio (III) formado durante la reacción del TOXM reducido con el dioxígeno.
Para aclarar el papel de este intermediario de diironio (III) como el oxidante activo en TOXM.
Investigar la reversibilidad de la activación del dioxígeno y el mecanismo de hidroxilación del sustrato.

Principales métodos:

Caracterización espectroscópica (óptica, Mössbauer) del intermediario diironio (III)
Estudios cinéticos de la desintegración intermedia y la hidroxilación del sustrato.
Análisis de la relación de energía libre lineal de la hidroxilación de fenol para-sustituido.

Principales resultados:

Se generó y caracterizó un intermediario transitorio de diironio (III).
La velocidad de descomposición del intermedio diiron (III) fue acelerada por el fenol, un sustrato de TOXM.
El peróxido de hidrógeno se generó durante la rotación en estado estacionario y se descompuso por la hidroxilasa oxidada, lo que indica una activación reversible del dioxígeno.
Un valor rho negativo en la relación lineal de energía libre confirmó el ataque electrófilo del oxidante sobre sustratos aromáticos.

Conclusiones:

El intermedio diironio (III) es el oxidante activo en el sistema TOXM.
Este intermedio es un peroxodieronio ((III) transitorio, a pesar de las diferencias espectroscópicas con otros centros conocidos.
Los hallazgos proporcionan evidencia convincente para el papel de este intermediario en el ciclo catalítico de TOXM.

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