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Estudio funcional de densidad del mecanismo de una tirosina fosfatasa: I. Formación intermedia en la formación
Dilipkumar Asthagiri1, Valerie Dillet, Tiqing Liu
1Department of Molecular Biology, TPC-15, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, California 92037, USA.
Journal of the American Chemical Society
|August 22, 2002
Resumen
Las fosfatasas de proteína tirosina catalizan las reacciones mediante la transferencia de grupos fosfato. Este estudio apoya una vía disociativa que involucra un sustrato dianiónico, con una barrera de energía más baja de la propuesta anterior.
Área de la Ciencia:
- La bioquímica es la bioquímica.
- Química computacional es la química computacional.
- Enzimología Enzimología.
Sus antecedentes:
- Las fosfatasas de proteína tirosina (PTP) son enzimas cruciales que regulan la señalización celular.
- El paso catalítico inicial involucra la fosfotransferencia de un sustrato a un sitio activo, la cisteína.
- Existe una ambigüedad mecanicista con respecto a la carga del sustrato (monoaniónico vs. dianiónico) y la vía de reacción (asociativo vs. disociativo).
Objetivo del estudio:
- Para dilucidar el mecanismo catalítico del primer paso en la actividad de la proteína tirosina fosfatasa.
- Para investigar la influencia de la carga del sustrato en la vía de reacción y la barrera de energía.
- Para modelar computacionalmente la reacción de fosfotransferencia dentro del entorno del sitio activo de la enzima.
Principales métodos:
- Cálculos funcionales combinados de densidad de grupos de sitios activos con modelado electrostático continuo.
- Barreras energéticas y geometrías calculadas para las vías de sustrato monoaniónico y dianiónico.
- Comparó las predicciones computacionales con la evidencia experimental existente.
Principales resultados:
- Se predijo una vía disociativa con transferencia temprana de protones para el sustrato dianiónico, produciendo una barrera de energía de 9 kcal / mol.
- Se predijo una vía asociativa con transferencia tardía de protones para el sustrato monoaniónico, produciendo una barrera de energía de 22 kcal / mol.
- La barrera predicha para la vía dianiónica se alinea mejor con las estimaciones experimentales (aprox. 14 kcal/mol). es decir, tiene 14 kcal/mol.
Conclusiones:
- Los hallazgos apoyan un mecanismo catalítico que involucra un sustrato dianiónico y una vía de reacción disociativa para las proteínas tirosina fosfatasas.
- Este mecanismo es consistente con los principios de la química orgánica clásica de las vías de reacción.
- El modelado computacional proporciona información valiosa sobre los mecanismos catalíticos de las enzimas.
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