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Mecanismo oxo asistido por agua para el metabolismo del hemo
Takashi Kamachi1, Kazunari Yoshizawa
1Institute for Materials Chemistry and Engineering, Kyushu University, Fukuoka 812-8581, Japan.
Journal of the American Chemical Society
|July 28, 2005
Resumen
La hemooxigenasa (HO) utiliza un mecanismo oxo asistido por agua para el metabolismo del hemo. Los estudios computacionales revelan que una molécula de agua puente reduce significativamente la barrera de activación para la oxidación del hemo, lo que permite una actividad enzimática eficiente.
Área de la Ciencia:
- La bioquímica es la bioquímica.
- Química computacional es la química computacional.
- Enzimología Enzimología.
Sus antecedentes:
- La hemooxigenasa (HO) es crucial para el metabolismo del hemo.
- Estudios anteriores sugirieron que las especies de hierro-hidroperoxo carecen de suficiente poder oxidante para la oxidación del hemo.
- Es esencial comprender el mecanismo preciso de la oxidación del hemo mediada por HO.
Objetivo del estudio:
- Para investigar el mecanismo del metabolismo del hemo por la hemo oxigenasa (HO) utilizando métodos computacionales.
- Para aclarar el papel de las especies de oxóferos de hierro y el entorno proteico en la oxidación del hemo.
- Proponer un mecanismo detallado para la oxidación del hemo catalizado por HO.
Principales métodos:
- Se emplearon cálculos de la teoría funcional de la densidad B3LYP.
- Los modelos incluían sistemas completos de protoporfirina IX y porfina.
- Se utilizaron cálculos de Mecánica Cuántica/Mecánica Molecular (QM/MM) para un modelo de enzima entera.
Principales resultados:
- Se confirmó que las especies de hierro-hidroperoxo eran insuficientes para la oxidación del hemo.
- Un mecanismo de ataque directo por oxo tiene una alta barrera de activación (49,8 kcal/mol) debido a la distorsión de la porfirina.
- Una molécula de agua puente reduce drásticamente la barrera de activación a 13,9 kcal / mol al minimizar la distorsión de la porfirina.
- Los cálculos QM / MM con un modelo de enzima completa confirmaron la importancia de la molécula de agua en el entorno de las proteínas.
Conclusiones:
- Se propone un mecanismo oxo asistido por agua para la oxidación del hemo por la hemooxigenasa.
- El entorno proteico, particularmente una molécula clave de agua, es crítico para facilitar la oxidación del hemo de baja barrera y regioselectiva.
- Los estudios computacionales proporcionan información significativa sobre el mecanismo enzimático de la oxigenasa del hemo.
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