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La catálisis mejorada con luz por la aspartato aminotransferasa dependiente del piridoxal fosfato
Melissa P Hill1, Elizabeth C Carroll, Mai C Vang
1Department of Chemistry, University of California, Davis, One Shields Avenue, Davis, California 95616, United States.
Journal of the American Chemical Society
|November 10, 2010
Resumen
Iluminar las enzimas dependientes de piridoxal 5'-fosfato (PLP) con luz azul mejora su actividad catalítica al promover la escisión de enlaces C-H. Esta fotoactivación es más pronunciada en las bases Schiff menos reactivas, revelando una nueva vía de estado triple.
Área de la Ciencia:
- La bioquímica es la bioquímica.
- La cinética de las enzimas.
- La fotoquímica es la fotoquímica.
Sus antecedentes:
- Las enzimas dependientes del piridoxal 5-fosfato (PLP) catalizan reacciones bioquímicas cruciales.
- La aspartato aminotransferasa (AAT) es una enzima clave dependiente de la PLP.
- Los intermediarios covalentes de aldimina externa son esenciales para los mecanismos enzimáticos dependientes de PLP.
Objetivo del estudio:
- Investigar el efecto de la excitación lumínica en la actividad catalítica de AAT.
- Para dilucidar el mecanismo de fotoactivación de la escisión de enlaces C-H en bases Schiff de PLP-aminoácidos.
- Para explorar el papel de los estados triplet en la vía de fotoactivación.
Principales métodos:
- Estudios sobre los efectos cinéticos de los isótopos.
- Análisis espectroscópico (de femtosegundos a minutos).
- Mediciones de actividad enzimática en estado de equilibrio bajo iluminación de luz azul.
Principales resultados:
- La excitación de la luz azul mejora significativamente la actividad catalítica de la AAT.
- El fotoaumento se atribuye a la aceleración de la desprotonación C-H de la aldimina externa.
- El grado de mejora se correlaciona con la reactividad intrínseca del enlace C-H.
- La fotoactivación implica un estado triplet con un pK (a) significativamente más bajo en comparación con el estado fundamental.
Conclusiones:
- La excitación de la luz se puede utilizar para modular la actividad de las enzimas dependientes de PLP.
- La fotoactivación proporciona una nueva vía para la escisión de enlaces C-H, distinta del mecanismo térmico.
- La comprensión de este mecanismo de fotoactivación podría conducir a nuevas estrategias para la ingeniería enzimática y el desarrollo de fármacos.
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