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Cambiar entre la esfera interna y la externa PCET Mecanismos de activación de moléculas pequeñas: desmutación de

Isabell Kenkel¹, Alicja Franke¹, Maximilian Dürr¹

¹Department of Chemistry and Pharmacy, University Erlangen-Nuremberg , 91058 Erlangen, Germany.

Journal of the American Chemical Society

|January 24, 2017

Resumen

Este estudio revela cómo las moléculas de agua son cruciales para la imitación de la enzima oxidorreducta, facilitando la transferencia de electrones acoplados a protones para la actividad de la superóxido dismutasa y permitiendo la reducción de oxígeno y superóxido en la esfera interna.

Área de la Ciencia:

Química bioorgánica
Imitación de enzimas
Catálisis de la oxidorreductaza

Sus antecedentes:

Las moléculas de agua en los sitios activos de la enzima a menudo se pasan por alto en los estudios de imitación de moléculas pequeñas.
La comprensión de la función de la oxidorreductasa con las especies reactivas es limitada.
Un complejo de manganeso (L^OH) imita la superóxido dismutasa (SOD) y responde al peróxido de hidrógeno.

Objetivo del estudio:

Investigar el papel del intercambio de agua en la reactividad de un imitador de SOD a base de manganeso.
Determinar las propiedades ácido-base, coordinación y redox del complejo.
Aclarar el mecanismo de la actividad y la transformación de SOD en una especie binuclear.

Principales métodos:

Titraciones potenciométricas
Espectrometría de masas a baja temperatura
Espectroscopia de RMN (dependiente de la temperatura y la presión)
La electroquímica
Análisis cinéticos de flujo detenido
Espectroscopia de resonancia paramagnética de electrones (EPR)
Análisis químico cuántico

Principales resultados:

El agua unida transitoriamente facilita la transferencia de electrones acoplados a protones (PCET) para la actividad SOD en la esfera externa.
La ausencia de agua permite la reducción de superóxido y oxígeno en la esfera interna.
El complejo se transforma en una especie binuclear Mn^II, manteniendo la actividad SOD contra los radicales hidroxilo y las especies Mn^IV-oxo.

Conclusiones:

Los ligandos de agua son esenciales para el mecanismo catalítico de los imitadores de superóxido dismutasa a base de manganeso.
El complejo exhibe una reactividad distinta basada en la coordinación del agua, lo que permite vías de transferencia de electrones tanto en la esfera externa como en la esfera interna.
El complejo de manganeso demuestra una actividad sólida de SOD y un mecanismo único de autorreparación en presencia de oxidantes fuertes.

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