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El oxirón (IV) en el compuesto cloroperoxidasa II es básico: implicaciones para la química de P450

Michael T Green¹, John H Dawson, Harry B Gray

¹Department of Chemistry, Pennsylvania State University, PA 16802, USA. mtg10@psu.edu

Science (New York, N.Y.)

|June 12, 2004

Resumen

El compuesto cloroperoxidasa II (CPO-II) presenta un enlace Fe-O más largo de lo esperado, que se asemeja a una unidad de ferril protonado. Este hallazgo sugiere un modelo potencial para los ciclos de oxigenación de P450, que impactan la oxigenación de hidrocarburos.

Área de la Ciencia:

La bioquímica es la bioquímica.
Química Inorgánica La Química Inorgánica es la química inorgánica.
La espectroscopia es una técnica de espectroscopia.

Sus antecedentes:

El compuesto cloroperoxidasa II (CPO-II) es un intermediario enzimático clave.
La comprensión de las propiedades electrónicas y estructurales de CPO-II es crucial para elucidar los mecanismos de reacción enzimática.

Objetivo del estudio:

Para investigar la longitud del enlace Fe-O y la basicidad de la unidad de ferril en CPO-II.
Para comparar hallazgos experimentales con predicciones computacionales.
Establecer el CPO-II como modelo para los intermediarios en los ciclos de oxigenación del P450.

Principales métodos:

Se empleó la espectroscopia de absorción de rayos X (XAS) para determinar la longitud del enlace Fe-O.
Los cálculos funcionales de densidad (DFT) se utilizaron para el modelado teórico y la comparación.

Principales resultados:

La longitud del enlace Fe-O en CPO-II se determinó experimentalmente para ser 1.82 (((1) Å.
Esta longitud de enlace es significativamente más larga que las unidades típicas de ferril y coincide estrechamente con los cálculos de DFT para un ferril protonado (Fe(IV) -OH).
La unidad de ferril en CPO-II exhibe una alta basicidad (pKa > 8,2), atribuida a la donación de electrones del ligando tiolato axial.

Conclusiones:

La unidad de ferril CPO-II, particularmente en su forma protonada, sirve como un modelo relevante para el intermediario de rebote en la oxigenación de P450.
Los radicales ferrílicos ligados al tiolato con valores elevados de pKa son capaces de oxigenar hidrocarburos saturados bajo condiciones fisiológicas relevantes para los huéspedes polipeptídicos.

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