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La tirosina 89 acelera la homólisis de los enlaces de carbono en la metilmalonilo-CoA mutasa
Monica D Vlasie1, Ruma Banerjee
1Biochemistry Department, University of Nebraska, Lincoln, Nebraska 68588-0664, USA.
Journal of the American Chemical Society
|May 2, 2003
Resumen
La metilmalonil-CoA mutaza utiliza Y89 para acelerar la escisión de los enlaces de carbono. La mutación de Y89 ralentiza significativamente la reacción, lo que indica que Y89 actúa como una cuña molecular, crucial para la catálisis enzimática.
Área de la Ciencia:
- La bioquímica es la bioquímica.
- La cinética de las enzimas.
- Biología estructural Biología estructural.
Sus antecedentes:
- La metilmalonil-CoA mutasa (MMCM) es una enzima crucial en el metabolismo.
- Cataliza el reordenamiento del metilmalonil-CoA en succinil-CoA.
- Esta reacción implica la escisión homolítica de un enlace cobalto-carbono en la adenosilcobalamina (AdoCbl).
Objetivo del estudio:
- Para investigar el papel del residuo de tirosina Y89 en el sitio activo en la catálisis de MMCM.
- Para aclarar el mecanismo por el cual Y89 contribuye a la eficiencia catalítica de la enzima.
Principales métodos:
- Se empleó mutagénesis dirigida al sitio para alterar el residuo de Y89.
- La cinética enzimática, incluidas las mediciones de k ((cat), se realizó en enzimas de tipo silvestre y mutantes.
- El análisis espectroscópico se utilizó para detectar intermediarios de reacción.
Principales resultados:
- La mutación de Y89 a fenilalanina o alanina dio como resultado una disminución de 1000 veces en la velocidad catalítica (k ((cat)).
- El efecto general del isótopo cinético fue suprimido en los mutantes Y89.
- Spectra indicó que la homólisis del enlace de co-carbono se convirtió en la tasa determinante en los mutantes.
Conclusiones:
- El residuo del sitio activo Y89 juega un papel crítico en la aceleración de la homólisis de enlaces de carbono.
- Y89 funciona como una "cuña molecular", facilitando la escisión del enlace Co-C.
- Estos hallazgos proporcionan una visión mecánica de la función de la metilmalonil-CoA mutasa.
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