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La transferencia de radicales oxilo e hidroxilo en la reducción de nitrito catalizado por el componente reductor de

Jing Yang¹, Logan J Giles¹, Christian Ruppelt²

¹†Department of Chemistry and Chemical Biology, The University of New Mexico, MSC03 2060, 1 University of New Mexico, Albuquerque, New Mexico 87131-0001, United States.

Journal of the American Chemical Society

|April 22, 2015

Resumen

La enzima del componente reductor de amidoxima mitocondrial (mARC) utiliza la resonancia paramagnética electrónica (EPR) y la computación para estudiar la reducción de nitrito. Se revela una vía sin barreras cuando se protona el nitrito, lo que facilita la transferencia de electrones.

Área de la Ciencia:

La bioquímica es la bioquímica.
Enzimología Enzimología.
Química computacional es la química computacional.

Sus antecedentes:

El componente reductor de amidoxima mitocondrial (mARC) es una enzima que contiene molibdeno y que participa en las reacciones redox.
Comprender el mecanismo catalítico del mARC, particularmente su interacción con el nitrito, es crucial para elucidar las vías de respiración celular.

Objetivo del estudio:

Para investigar las coordenadas de reacción para la reducción de un electrón de nitrito por la enzima mARC.
Para aclarar el papel del molibdeno unido a la enzima y la protonación del sustrato en el mecanismo catalítico.

Principales métodos:

Espectroscopia combinada de resonancia paramagnética de electrones (EPR) para detectar especies paramagnéticas.
Enfoques computacionales, incluido el análisis de órbitas de fragmentos, para modelar vías de reacción y barreras.

Principales resultados:

Una especie paramagnética de Mo(V) se genera al reaccionar el mARC reducido con nitrito.
Los parámetros hiperfinos de EPR indican similitud entre mARC y la sulfitooxidasa.
Se evaluaron dos mecanismos de reducción: una barrera modesta (14 kcal/mol) para el nitrito no protonado y una vía sin barreras para el nitrito protonado.

Conclusiones:

La protonación de nitrito próximo al centro de molibdeno permite una conversión catalítica sin barreras.
La alta covalencia Mo-O-H-N-O facilita la transferencia de electrones a través de una vía orbital π.
Las restricciones orbitales identificadas y los mecanismos catalíticos son relevantes para el mARC y otras enzimas de piranopterina molibdeno.

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