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Mecanismo para la escisión del anillo de catecol por las dioxigenasas de extradiol de hierro no hemo
Per E M Siegbahn1, Fredrik Haeffner
1Department of Physics, Stockholm Centre for Physics, Astronomy and Biotechnology (SCFAB), Stockholm University, S-106 91 Stockholm, Sweden. ps@physto.se
Journal of the American Chemical Society
|July 22, 2004
Resumen
Las dioxigenasas de extradiol de hierro no hemo utilizan un mecanismo catalítico único que implica cambios en el estado de espín y un intermediario parcialmente aniónico. Este carácter aniónico es clave para la selectividad de la enzima en la escisión de enlaces C-C de catecol.
Área de la Ciencia:
- La bioquímica es la bioquímica.
- Química computacional es la química computacional.
- Enzimología Enzimología.
Sus antecedentes:
- Las dioxigenasas de extradiol de hierro no hemo catalizan la escisión de los catecolos.
- Estas enzimas difieren de las intradiol-dioxigenasas en su sitio de escisión del enlace C-C.
- Comprender su mecanismo catalítico es crucial para las aplicaciones bioquímicas.
Objetivo del estudio:
- Para dilucidar el mecanismo catalítico de las dioxigenasas de extradiol de hierro no hemo.
- Investigar el papel de las transiciones de estado de espín y los intermediarios del sustrato.
- Para determinar los factores que influyen en la selectividad de las enzimas.
Principales métodos:
- Cálculos de la teoría funcional de la densidad híbrida (DFT).
- Desarrollo de modelos químicos detallados del sitio activo de la enzima (aprox. tiene 70 átomos).
- La inclusión de los ligandos de la primera y segunda cáscara, incluidos los residuos de histidina, glutamato, aspartato y tirosina.
Principales resultados:
- El catecol se une como un monoanión, y el dioxígeno reemplaza un ligando de agua.
- Una transición de giro del estado de setto al quinteto facilita la formación de peróxido.
- La escisión del enlace O-O forma un intermedio clave con carácter mixto de radicales y aniones.
Conclusiones:
- El carácter parcialmente aniónico del sustrato intermedio dicta la selectividad de la enzima.
- Los hallazgos computacionales se alinean con los datos experimentales existentes.
- El estudio proporciona información sobre el ciclo catalítico de la extradiol-dioxigenasa de hierro no hemo.
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