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Modificación de hemo protésico durante la oxidación de iones de haluro. Demostración de la oxidación del cloruro por
Liusheng Huang1, Grzegorz Wojciechowski, Paul R Ortiz de Montellano
1Department of Pharmaceutical Chemistry, University of California, 600 16th Street, San Francisco, California 94143-2280, USA.
Journal of the American Chemical Society
|April 14, 2005
Resumen
La peroxidasa del rábano picante (HRP) ahora puede oxidar el cloruro y el bromuro, formando grupos hemo modificados. Este hallazgo sugiere que se necesitan cambios mínimos para que las peroxidasas obtengan habilidades únicas de oxidación de cloruro.
Área de la Ciencia:
- La bioquímica es la bioquímica.
- Enzimología Enzimología.
Sus antecedentes:
- La mieloperoxidasa (MPO), la eosinófila peroxidasa (EPO) y la cloroperoxidasa oxidan los haluros, a diferencia de la mayoría de las peroxidasas como la peroxidasa del rábano picante (HRP).
- La HRP típicamente oxida sólo el yoduro y algunas veces el bromuro.
Objetivo del estudio:
- Para investigar la oxidación del bromuro (Br-) y el cloruro (Cl-) por HRP.
- Explorar el mecanismo de la oxidación de haluros por HRP y sus implicaciones para la modificación del hemo.
Principales métodos:
- Incubación de HRP con Br- o Cl- y peróxido de hidrógeno (H2O2) a pH ácido.
- Espectrometría de masas para analizar las modificaciones del grupo hemo.
- Comparación con reacciones de hemo libres de proteínas y reacciones a pH neutro.
Principales resultados:
- El HRP a pH ácido cataliza la brominación y modifica su grupo hemo con bromuro, formando aductos de bromohidrina.
- Modificaciones similares del hemo, incluyendo un adducto de meso-cloro, ocurren cuando el HRP reacciona con Cl- y H2O2.2.
- Estas modificaciones dependen del pH y de la presencia de la proteína HRP.
Conclusiones:
- HRP demuestra la capacidad de oxidar Cl- por primera vez.
- La modificación de hemo protésico durante la oxidación de halogenuros por HRP sugiere que se requiere un ajuste mínimo de proteínas para la actividad similar a la MPO/EPO.
- El estudio plantea preguntas sobre cómo las hemas de MPO y EPO evitan la auto-modificación durante la oxidación de haluros.
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