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Las etapas de túneles de hidrógeno en la catálisis de la ciclooxigenasa-2
Husain H Danish1, Irina S Doncheva, Justine P Roth
1Department of Chemistry, Johns Hopkins University, 3400 North Charles Street, Baltimore, Maryland 21218, United States.
Journal of the American Chemical Society
|September 10, 2011
Resumen
La actividad de la enzima ciclooxigenasa-2 (COX-2) se estudió utilizando ácido linoleico. Los investigadores observaron efectos significativos del isótopo cinético del deuterio, lo que indica un túnel de hidrógeno reversible durante el proceso de oxidación.
Área de la Ciencia:
- La bioquímica es la bioquímica.
- Enzimología Enzimología.
- La cinética química es la cinética química.
Sus antecedentes:
- Las ciclooxigenasas-1 y -2 (COX-1 y COX-2) son hemoproteínas que utilizan radicales tirosílicos para sintetizar autocoides derivados de lípidos.
- La COX-2 es un mediador clave de la inflamación y a menudo está regulada al alza en varios tipos de cáncer.
Objetivo del estudio:
- Para investigar la oxidación catalizada por COX-2 del ácido linoleico, un análogo de sustrato.
- Para dilucidar el mecanismo de la abstracción del átomo de hidrógeno y el papel del radical catalítico tirosilo.
Principales métodos:
- Estudios de cinética enzimática utilizando ácido linoleico como análogo de sustrato.
- Medición de los efectos del isótopo cinético del deuterio (KIEs) bajo diferentes concentraciones de oxígeno.
- Análisis de la dependencia de la temperatura de las KIEs.
Principales resultados:
- Se observaron muy grandes (≥20) KIEs de deuterio independientes de la temperatura para la rotación de enzimas, atribuidas a la abstracción de átomos de hidrógeno del C-H bisálico (D) del ácido linoleico.
- La magnitud de KIE dependía de la concentración de O2 sugiriendo un túnel H/D reversible mediado por el radical catalítico tirosilo.
- En los niveles fisiológicos de O2 se observaron KIEs dependientes de la temperatura en la homólisis de O-H2D, consistentes con el túnel nuclear.
Conclusiones:
- El estudio proporciona nuevos conocimientos sobre el mecanismo de oxidación de ácidos grasos catalizados por COX-2.
- La evidencia apoya la participación del túnel de hidrógeno reversible mediado por el radical catalítico tirosilo en la función COX-2.
- Los hallazgos contribuyen a comprender el papel de la COX-2 en la inflamación y la biología del cáncer.
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