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Conocimientos fundamentales sobre la transferencia de electrones acoplados a protones en la lipoxigenasa de soja a
Pengfei Li1,2, Alexander V Soudackov1,2, Sharon Hammes-Schiffer1,2
1Department of Chemistry, University of Illinois at Urbana-Champaign , 600 South Mathews Avenue, Urbana, Illinois 61801, United States.
Journal of the American Chemical Society
|February 3, 2018
Resumen
Lipoxigenasa de soja y sus derivados
Área de la Ciencia:
- Bioquímica y Biofísica
- Enzimología
- Química computacional
Sus antecedentes:
- Las reacciones de transferencia de electrones acoplados a protones (PCET) son cruciales en los sistemas biológicos.
- La lipoxigenasa de soja (SLO) cataliza una reacción PCET prototipo, vital para comprender el túnel de hidrógeno enzimático.
- Los efectos cinéticos experimentales de los isótopos (KIE) para el tipo silvestre (WT) y el doble mutante (DM) SLO proporcionan datos clave.
Objetivo del estudio:
- Investigar el mecanismo de reacción PCET en SLO utilizando simulaciones computacionales avanzadas.
- Para aclarar los factores que contribuyen a las diferencias experimentalmente observadas en las KIE entre WT y DM SLO.
- Para correlacionar las propiedades estructurales y electrónicas con la eficiencia del túnel de hidrógeno.
Principales métodos:
- Se utilizaron simulaciones mixtas de energía libre cuántica/clásica (QM/MM).
- Se calcularon las superficies de energía libre y los potenciales de fuerza media (PMF).
- Se analizaron la falta de armonía y los efectos electrostáticos que influyen en la reacción PCET.
Principales resultados:
- Las simulaciones reproducen con precisión los KIEs experimentales para WT (∼80) y DM (∼700) SLO.
- La reacción PCET es exergética para WT y ligeramente endoergética para DM.
- Una mayor distancia C-O de equilibrio en DM, debido a la unión del sustrato en una cavidad expandida, aumenta significativamente el KIE.
Conclusiones:
- La cavidad de unión expandida en el DM es el principal impulsor de su KIE superior.
- Los potenciales anharmónicos y los campos electrostáticos locales facilitan el túnel de hidrógeno eficiente.
- Si bien el entorno proteico ayuda a la alineación del sustrato, la electrostática local es clave para el PCET y el túnel.
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