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La hidrólisis del monoester de fosfato en el ciclohexano.
Randy B Stockbridge1, Richard Wolfenden
1Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27514, USA.
Journal of the American Chemical Society
|December 24, 2009
Resumen
La hidrólisis del monoester de fosfato catalizado por enzimas es un reto. La transferencia de sustratos del agua al ciclohexano mejora drásticamente las tasas de hidrólisis, principalmente debido al aumento de la entropía de activación.
Área de la Ciencia:
- La bioquímica es la bioquímica.
- La cinética química es la cinética química.
- Catalización de enzimas por catálisis enzimática.
Sus antecedentes:
- La hidrólisis del monoester de fosfato es una reacción difícil, a menudo catalizada por enzimas.
- La catálisis enzimática puede implicar la extracción del sustrato de la solución acuosa.
- Las fosfohidrolasas son enzimas que catalizan la hidrólisis de los ésteres de fosfato.
Objetivo del estudio:
- Investigar el efecto de la transferencia de sustratos de monoéster de fosfato del agua a un disolvente orgánico en las tasas de hidrólisis.
- Para determinar si la extracción del sustrato influye en los efectos catalíticos observados en la actividad de la fosfohidrolasa.
Principales métodos:
- Sintetizó la sal de tetrabutylammonium del fosfato de neopentyl.
- Se disolvió la sal en ciclohexano húmedo para lograr velocidades de hidrólisis medibles.
- Se midió la constante de velocidad de segundo orden para la hidrólisis en el disolvente orgánico.
Principales resultados:
- La sal de tetrabututilamonio del fosfato de neopentilo disuelto en ciclohexano húmedo en concentraciones medibles.
- La constante de velocidad de hidrólisis para el dianión fosfomonoester se incrementó aproximadamente 2 x 10 12 veces al transferirse del agua al ciclohexano.
- Esta mejora de la velocidad se atribuyó a un aumento en la entropía de activación.
Conclusiones:
- La extracción de sustratos de monoésteres de fosfato del agua en un disolvente no polar mejora significativamente las tasas de hidrólisis.
- La mejora de la tasa observada se debe principalmente a los cambios entrópicos favorables tras la transferencia.
- Este hallazgo apoya la hipótesis de que la partición del sustrato juega un papel crucial en la eficiencia catalítica de las fosfohidrolasas.
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