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Un triptófano ionizable en el sitio activo imparte actividad de catalasa a un núcleo de peroxidasa

Peter C Loewen¹, Xavi Carpena, Pietro Vidossich

¹Department of Microbiology, University of Manitoba , Winnipeg MB R3T 2N2, Canada.

Journal of the American Chemical Society

|May 3, 2014

Resumen

Las peroxidasas catalasas (KatG) desproporcionan el peróxido de hidrógeno a través de la desprotonación de Trp en el sitio activo, imitando a las catalasas monofuncionales. Una arginina móvil actúa como un interruptor electrónico, controlando este paso catalítico crucial.

Área de la Ciencia:

La bioquímica es la bioquímica.
Biología Estructural Biología estructural.
Enzimología Enzimología.

Sus antecedentes:

Las peroxidasas de catalasa (KatG) son proteínas hemo bifuncionales.
KatG muestra actividad catalítica, desproporcionando el peróxido de hidrógeno.
Poseen diferencias estructurales en comparación con las catalasas monofuncionales.

Objetivo del estudio:

Para dilucidar el mecanismo de la reacción catalítica en KatG.
Para entender el papel de los residuos del sitio activo en la función de KatG.
Para comparar el mecanismo de KatG con el de las catalasas monofuncionales.

Principales métodos:

Se empleó cristalografía de rayos X para determinar la estructura de KatG.
Se realizaron cálculos de mecánica cuántica / mecánica molecular (QM / MM).
Se integraron datos estructurales y computacionales para analizar el mecanismo de reacción.

Principales resultados:

El mecanismo de reacción cataláctica implica la desprotonación del triptófano (Trp) en el sitio activo.
Este sitio activo Trp funciona de manera análoga a la Histidina distal (His) en las catalasas monofuncionales.
Un residuo móvil de arginina interactúa con un adducto Met-Tyr-Trp, actuando como un interruptor electrónico.

Conclusiones:

El estudio revela un nuevo mecanismo catalítico para KatG que involucra la desprotonación de Trp.
La arginina móvil juega un papel regulador clave en la activación del sitio catalítico.
La estructura única de KatG permite la actividad catalítica a través de un mecanismo distinto de las catalasas monofuncionales.

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