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Estudios espectroscópicos y computacionales de la nitrita reductasa: transferencia de electrones inducida por

Somdatta Ghosh¹, Abhishek Dey, Yan Sun

¹Department of Chemistry, Stanford University, Stanford, California 94305, USA.

Journal of the American Chemical Society

|December 5, 2008

Resumen

La protonación desencadena la transferencia de electrones en Rhodobacter sphaeroides nitrito reductasa, lo que lleva a la generación de NO. La unión del nitrito bidentado al cobre activa la escisión de enlaces, crucial para la reducción del nitrito.

Área de la Ciencia:

Bioquímica y Biofísica.
Química bioorgánica Química bioorgánica.
Química computacional es la química computacional.

Sus antecedentes:

La nitrito reductasa (NiR) de Rhodobacter sphaeroides contiene centros de cobre tipo 1 (T1) y tipo 2 (T2).
El sitio de cobre T2 se une al nitrito, un sustrato para la reducción.
Comprender el mecanismo de reducción del nitrito es crucial para la función de la enzima.

Objetivo del estudio:

Para dilucidar la estructura geométrica y electrónica del sitio de cobre T2 ligado al nitrito en NiR.
Investigar el mecanismo dependiente del pH de la reducción del nitrito, incluida la transferencia de electrones y la escisión del enlace N-O.
Determinar el papel de la unión del nitrito y la coordinación del cobre en el proceso catalítico.

Principales métodos:

Técnicas experimentales combinadas: Espectroscopia (por ejemplo, UV-Vis, EPR) para sondear los centros de cobre.
Cálculos teóricos: Teoría Funcional de Densidad (DFT) para modelar la estructura electrónica y las vías de reacción.
Estudios dependientes del pH para correlacionar los estados de protonación con la actividad enzimática y la transferencia de electrones.

Principales resultados:

A un pH alto, no se produce ninguna transferencia de electrones desde el T1 reducido al cobre T2 ligado al nitrito.
La protonación a un pH bajo desencadena la transferencia de electrones de T1 a T2, iniciando la generación de NO.
Los cálculos de DFT revelan que la transferencia de protones precede y desencadena la transferencia de electrones para la escisión del enlace N-O.
La unión del nitrito bidentato al cobre es clave para activar la escisión reductora, que implica la unión posterior y la estabilización del producto.

Conclusiones:

El mecanismo de reducción de nitrito por NiR implica un proceso de transferencia de electrones acoplados a protones.
La coordinación de nitrito bidentato con el sitio de cobre T2 es esencial para la catálisis.
El comportamiento dependiente del pH es crítico para regular la transferencia de electrones y la formación de NO.

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