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La acumulación de los intermediarios tetraédricos en la catálisis de la colinesterasa: un estudio de efecto isotópico
Jose R Tormos1, Kenneth L Wiley, Yi Wang
1The University of Iowa, Department of Chemistry, Iowa City, Iowa 52242, United States.
Journal of the American Chemical Society
|November 26, 2010
Resumen
Este estudio revela que el intermediario tetraédrico se acumula durante la hidrólisis de acetiltiocolina por Drosophila melanogaster acetilcolinesterasa (DmAChE). Los experimentos de efecto isotópico aclaran los estados de transición involucrados en la catálisis de DmAChE.
Área de la Ciencia:
- La bioquímica es la bioquímica.
- La cinética de las enzimas.
- La cinética de las sustancias químicas.
Sus antecedentes:
- La catálisis de la acetiltiocolina por la butirilcolinesterasa humana (BuChE) incluye un intermediario tetraédrico.
- Las acetilcolinesterasas (AChE) son enzimas cruciales en la neurotransmisión.
- La comprensión de los mecanismos catalíticos de AChE es vital para el desarrollo de fármacos y la comprensión de la función enzimática.
Objetivo del estudio:
- Para investigar el mecanismo catalítico de la Drosophila melanogaster acetilcolinesterasa (DmAChE) utilizando acetiltiocolina como sustrato.
- Para determinar el papel y la acumulación del intermedio tetraédrico en la catálisis de DmAChE.
- Para caracterizar los estados de transición involucrados en la hidrólisis catalizada por DmAChE.
Principales métodos:
- Análisis cinético de la hidrólisis de la acetiltiocolina por DmAChE.
- Medición de los efectos del isótopo cinético secundario de β-deuterio en diferentes concentraciones de sustrato.
- Determinación de los efectos isotópicos del disolvente y los inventarios de protones para caracterizar los estados de transición.
Principales resultados:
- La acumulación de un intermediario tetraédrico fue respaldada por experimentos de efecto isotópico en catálisis DmAChE.
- La inhibición del sustrato se observó en altas concentraciones de sustrato, a diferencia de la catálisis de BuChE.
- Los efectos de isótopos cinéticos indicaron cambios de hibridación distintos durante los estados de transición de acilación y desacilación.
- Los efectos de isótopos de disolventes y los inventarios de protones sugirieron la estabilización del estado de transición intermedio tetraédrico por múltiples interacciones protónicas.
Conclusiones:
- Los hallazgos apoyan un mecanismo que involucra un intermediario tetraédrico estable en la catálisis de DmAChE.
- Se caracterizaron distintos estados de transición para la acilación y la desacilación, lo que proporciona información sobre la eficiencia de las enzimas.
- Se propone un modelo que resalta la contribución de la estabilización intermedia tetraédrica al poder catalítico de la acetilcolinesterasa.
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