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La primera prueba experimental de la hipótesis de que las enzimas han evolucionado para mejorar el túnel de hidrógeno
Kenneth M Doll1, Bruce R Bender, Richard G Finke
1Department of Chemistry, Colorado State University, Fort Collins, Colorado 80523, USA.
Journal of the American Chemical Society
|September 4, 2003
Resumen
Este estudio probó si las enzimas mejoran el túnel cuántico, encontrando que una enzima dependiente de la coenzima B12 no mejora el túnel de hidrógeno. En su lugar, la enzima utiliza el mismo túnel cuántico observado en reacciones libres de enzimas.
Área de la Ciencia:
- La bioquímica es la bioquímica.
- Química Física es la química física.
- Catalización de enzimas por catálisis enzimática.
Sus antecedentes:
- La catálisis enzimática puede implicar el túnel mecánico cuántico.
- La hipótesis de un túnel mejorado impulsado por enzimas requiere pruebas experimentales.
- Las enzimas dependientes de la adenosilcobalamina (AdoCbl) son cruciales en las reacciones biológicas.
Objetivo del estudio:
- Para probar experimentalmente la hipótesis de que las enzimas mejoran el túnel mecánico cuántico.
- Para comparar el túnel de hidrógeno en reacciones dependientes de AdoCbl con y sin la enzima.
- Para investigar el papel del túnel cuántico en las reacciones del modelo de la diol deshidratasa.
Principales métodos:
- Se estudió la abstracción de átomos H/D del etilenoglicol utilizando radicales Ado(*) y 8-MeOAdo(*).
- Radicales generados a través de la termólisis Co-C de los precursores de AdoCbl y 8-MeOAdoCbl.
- Se midieron los efectos del isótopo cinético del deuterio (KIEs) en un rango de temperatura (80-120°C).
Principales resultados:
- Se observó un túnel mecánico cuántico significativo en reacciones libres de enzimas.
- Los KIE medidos y los parámetros derivados ([E(D) - E(H) ], A(H) /A(D)) indicaron un túnel sustancial.
- Los datos de las reacciones enzimáticas y libres de enzimas fueron idénticos dentro del límite de error experimental.
Conclusiones:
- La enzima dependiente de AdoCbl estudiada no mejora el túnel mecánico cuántico.
- La enzima utiliza el inherente túnel cuántico presente en las reacciones basadas en soluciones.
- Las reacciones enzimáticas y libres de enzimas exhiben alturas y anchos de barrera similares para la abstracción de H.
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