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Published on: May 22, 2016
La inactivación de la acetil-CoA sintasa / monóxido de carbono deshidrogenasa por el cobre
Matthew R Bramlett1, Xiangshi Tan, Paul A Lindahl
1Department of Biochemistry and Biophysics, Texas A&M University, College Station, Texas 77843, USA.
Journal of the American Chemical Society
|August 2, 2003
Resumen
El cobre no es esencial para la catálisis de la acetil-CoA sintasa (ACS). En cambio, el cobre inactiva el ACS al unirse al sitio activo, evitando la transferencia crucial del grupo metilo y bloqueando las señales espectroscópicas clave.
Área de la Ciencia:
- La bioquímica es la bioquímica.
- Catalización de enzimas por catálisis enzimática.
- Química bioorgánica Química bioorgánica.
Sus antecedentes:
- Las recientes estructuras cristalinas de la acetil-CoA sintasa (ACS) de Moorella thermoacetica revelaron diferentes composiciones y geometrías metálicas en el sitio activo (A-cluster).
- Estas variaciones estructurales provocaron propuestas para dos mecanismos catalíticos distintos: uno basado en níquel y otro basado en cobre.
Objetivo del estudio:
- Investigar el papel del cobre en la actividad y el mecanismo de la acetil-CoA sintasa (ACS).
- Para determinar si el cobre es necesario para la catálisis o si actúa como inhibidor.
Principales métodos:
- Pruebas enzimáticas que miden la actividad de transferencia de grupos sintasa y metilo.
- Análisis del contenido de metales en el ACS purificado.
- Espectroscopia de resonancia paramagnética de electrones (EPR), incluidas las muestras tratadas con CO.
Principales resultados:
- El cobre no es necesario para la catálisis de la acetil-CoA sintasa (ACS).
- El cobre inactiva el ACS al unirse al sitio proximal del cúmulo A.
- La unión del cobre impide la aceptación del grupo metilo de la proteína corrinoide-hierro-azufre y bloquea la señal EPR característica del NiFeC.
Conclusiones:
- El mecanismo catalítico basado en el cobre propuesto para el ACS es poco probable.
- El cobre actúa como un inhibidor de la ACS, interfiriendo con la unión al sustrato y la rotación catalítica.
- Se apoya el mecanismo basado en Ni, con el cobre identificado como un contaminante perjudicial.
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