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¿Cuánto ganan realmente las enzimas al restringir sus fragmentos en reacción?
1Department of Chemistry, University of Southern California, Los Angeles, California 90089-1062, USA.
Journal of the American Chemical Society
|April 11, 2002
Resumen
Los efectos estéricos no son el principal impulsor de la catálisis enzimática. Las simulaciones por computadora revelan que las interacciones electrostáticas, no las fuerzas estéricas, son la clave para la haloalcana-dehalogenasa.
Área de la Ciencia:
- La bioquímica es la bioquímica.
- Química computacional es la química computacional.
- Catalización de enzimas por catalización de enzimas
Sus antecedentes:
- La catálisis enzimática a menudo se atribuye a los efectos estéricos, empujando los sustratos a una configuración de ataque cercano (NAC).
- El papel de las contribuciones estéricas frente a las fuerzas electrostáticas en la catálisis enzimática sigue siendo objeto de investigación.
- La haloalcana dehalogenasa sirve como una enzima modelo para el estudio de los mecanismos catalíticos.
Objetivo del estudio:
- Evaluar cuantitativamente la importancia relativa de los efectos estéricos en la catálisis enzimática utilizando simulaciones por computadora.
- Para diferenciar entre las contribuciones estéricas y electrostáticas al poder catalítico de la haloalcana deshalogenasa.
Principales métodos:
- Utilizó el método de enlace de valencia empírico (EVB) para modelar superficies de potencial de reacción.
- Se emplearon ciclos termodinámicos para comparar las reacciones enzimáticas con las reacciones en el agua.
- Desarrolló dos estrategias computacionales: restricciones de sustrato en agua y eliminación de interacciones electrostáticas.
Principales resultados:
- Se encontró que la contribución no electrostática (esterica) a la catálisis fue de aproximadamente -0,7 kcal/mol.
- El efecto estérico aparente, incluyendo las contribuciones electrostáticas, fue de -2,2 kcal/mol.
- Las interacciones electrostáticas representaron la mayor parte del efecto catalítico, aproximadamente -6.1 kcal/mol.
Conclusiones:
- Los efectos estéricos no son la principal fuente de poder catalítico en la haloalcana dehalogenasa.
- Las interacciones electrostáticas juegan un papel dominante en la eficiencia catalítica de la enzima.
- El efecto estérico aparente está significativamente influenciado por la energía de reorganización del disolvente, desafiando las opiniones tradicionales.
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