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Published on: December 19, 2011
El sitio activo de la arsenita oxidasa de Alcaligenes faecalis
Thomas Conrads1, Craig Hemann, Graham N George
1Department of Biochemistry, The Ohio State University, Columbus, Ohio 43210, USA.
Journal of the American Chemical Society
|September 19, 2002
Resumen
La arsenita oxidasa, una enzima de molibdeno, tiene estructuras de cofactores únicas. Su sitio activo revela distintas dinámicas de enlace Mo-S y aromaticidades de pterina, lo que sugiere un papel estructural intermedio en la evolución de la enzima del molibdeno.
Área de la Ciencia:
- La bioquímica es la bioquímica.
- La cinética de las enzimas.
- Biología estructural Biología estructural.
Sus antecedentes:
- La arsenita oxidasa es una enzima clave en la oxidación del arsénico, perteneciente a la familia de las DMSO reductasas de las enzimas de molibdeno.
- Las enzimas de molibdeno utilizan cofactores de molibdopterina para su actividad catalítica, con variaciones estructurales que influyen en la función.
Objetivo del estudio:
- Para dilucidar las propiedades estructurales y electrónicas del sitio activo en la arsenita oxidasa.
- Comprender el papel de los cofactores de molibdeno y su entorno de coordinación durante la reducción enzimática.
Principales métodos:
- Se empleó la espectroscopia de absorción de rayos X (XAS) para sondear las distancias de enlace molibdeno-ligando y los estados de oxidación.
- Se utilizó la espectroscopia Raman de resonancia para investigar la estructura electrónica y la aromaticidad de los cofactores de pterina.
Principales resultados:
- XAS reveló un acortamiento de los enlaces Mo-S en la reducción y la presencia de un oxoligando, con un enlace Mo-O transitorio en el estado oxidado.
- La espectroscopia Raman de resonancia indicó una aromaticidad diferencial entre las dos fracciones de pterin-ditioleno (Q-pterin y P-pterin).
Conclusiones:
- Las propiedades estructurales y electrónicas de la arsenita oxidasa sugieren un estado intermedio entre las típicas enzimas de molibdeno y las enzimas de tungsteno.
- Las distintas estructuras de pterina y la dinámica de enlaces Mo-S contribuyen al mecanismo catalítico y al posicionamiento evolutivo de la enzima.
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