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Cómo la solución del sustrato contribuye a la enantioselectividad de la subtilisina hacia los alcoholes secundarios
Christopher K Savile1, Romas J Kazlauskas
1Department of Chemistry, McGill University, 801 Sherbrooke Street West, Montréal, Québec, Canada, H3A 2K6.
Journal of the American Chemical Society
|September 1, 2005
Resumen
La subtilisin es una sustancia
Área de la Ciencia:
- Biocatálisis e Ingeniería de Enzimas.
- Química orgánica es la química orgánica.
- Estructura y función de las proteínas.
Sus antecedentes:
- La regla establecida para predecir la enantioselectividad de la subtilisina en reacciones secundarias con alcohol asume dos bolsas de sitio activo para los sustituyentes.
- Los datos experimentales, incluida la cristalografía de rayos X, contradicen esta regla, revelando solo un bolsillo (S1') adecuado para un grupo de tamaño fenilo.
- La regla existente con frecuencia predice erróneamente la enantioselectividad en ambientes acuosos.
Objetivo del estudio:
- Resolver las contradicciones en la predicción de la enantioselectividad de la subtilisina hacia los alcoholes secundarios.
- Para refinar la regla empírica que rige las interacciones enzima-sustrato en la biocatálisis.
- Aclarar el papel de las propiedades de los sustituyentes en las reacciones enantioselectivas catalizadas por enzimas.
Principales métodos:
- Cristalografía de rayos X de la subtilisina para analizar la estructura del sitio activo.
- Estudios cinéticos de enzimas con una serie de alcoholes secundarios en solución acuosa.
- Análisis de correlación entre la enantioselectividad y la hidrofobidad del sustituto (log P/P0).
Principales resultados:
- El sitio activo de la subtilisina (bolsa S1') contiene sólo un sustituto de los alcoholes secundarios.
- El otro sustituto es expuesto y solvado por el disolvente acuoso.
- La enantioselectividad mostró una correlación lineal con la diferencia de hidrofobidad entre los dos sustituyentes.
Conclusiones:
- La regla refinada postula que la subtilisina se une a un sustituyente, dejando el otro en el disolvente.
- La diferencia de hidrofobidad de los sustitutos es un factor clave que determina la enantioselectividad en el agua.
- Este hallazgo proporciona un modelo más preciso para predecir las reacciones enantioselectivas catalizadas por enzimas.
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