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Prueba de discriminación geométrica dentro de un sitio activo de la enzima: enlace de hidrógeno restringido en el
Paul A Sigala1, Daniel A Kraut, Jose M M Caaveiro
1Department of Biochemistry, Stanford University, Stanford, California 94305, USA.
Journal of the American Chemical Society
|September 24, 2008
Resumen
Las enzimas controlan con precisión la unión del sustrato a través de sutil geometría del sitio activo. Este estudio revela cómo las limitaciones estructurales menores impactan significativamente la catálisis enzimática y la estabilización de la energía.
Área de la Ciencia:
- La bioquímica es la bioquímica.
- Biología Estructural Biología estructural.
- La cinética de las enzimas.
Sus antecedentes:
- Las enzimas aceleran las reacciones optimizando la unión del sitio activo para los estados de transición.
- Comprender la escala de distancia precisa y el impacto energético de las restricciones del sitio activo es crucial para la catálisis enzimática.
- La flexibilidad y las capacidades de discriminación geométrica de los sitios activos de la enzima siguen siendo preguntas clave de investigación.
Objetivo del estudio:
- Para investigar la escala de distancia de las restricciones mediadas por la fuerza no covalente en las cadenas laterales y los ligandos dentro de los sitios activos de la enzima.
- Determinar las consecuencias energéticas de las restricciones geométricas en la isomerasa cetosteroide bacteriana (KSI).
- Para probar cómo las enzimas distinguen e influyen energéticamente en los reordenamientos estructurales del sustrato.
Principales métodos:
- Cristalografía de rayos X de alta resolución (1.2-1.5 A de resolución).
- Espectroscopia de Resonancia Magnética Nuclear (RMN) ((1) H y (19) F).
- Cálculos mecánicos cuánticos y mediciones de unión analógica del estado de transición.
Principales resultados:
- Las interacciones del sitio activo de KSI limitan la reorientación de la cadena lateral local y evitan el acortamiento del enlace de hidrógeno (<0,1 A).
- Estas sutiles restricciones geométricas afectan significativamente la energía de unión de ligandos.
- La geometría restringida estabiliza la carga negativa dentro del agujero de oxyanión, impactando la catálisis.
Conclusiones:
- Los sitios activos de la enzima utilizan efectos geométricos sutiles, a menudo por debajo de la resolución cristalográfica típica, para lograr la eficiencia catalítica.
- Las fuerzas no covalentes juegan un papel crítico en la aplicación de arreglos estructurales precisos para una función óptima de la enzima.
- Los enfoques experimentales sinérgicos son esenciales para diseccionar los complejos mecanismos de la catálisis enzimática.
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