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Estructura del estado de transición de la 5'-metiltioadenosina fosforilasa humana en su estado de transición
Vipender Singh1, Vern L Schramm
1Department of Biochemistry, Albert Einstein College of Medicine, Bronx, New York 10461, USA.
Journal of the American Chemical Society
|November 9, 2006
Resumen
Este estudio utilizó efectos de isótopos cinéticos y modelado por computadora para revelar el estado de transición de la 5'-metiltioadenosina fosforilasa humana (MTAP). Los hallazgos indican un estado de transición S(N) 1 tardío con una participación significativa de nucleófilos de fosfato.
Área de la Ciencia:
- La bioquímica es la bioquímica.
- La cinética de las enzimas.
- Química computacional es la química computacional.
Sus antecedentes:
- La 5-metiltioadenosina fosforilasa humana (MTAP) es una enzima crucial en el metabolismo de las purinas.
- Comprender el mecanismo catalítico y el estado de transición de la MTAP es vital para el desarrollo de fármacos.
Objetivo del estudio:
- Para dilucidar la estructura del estado de transición del MTAP humano utilizando efectos de isótopos cinéticos (KIEs) y modelado de la teoría funcional de la densidad (DFT).
- Para determinar el mecanismo de reacción e identificar las interacciones clave en el estado de transición.
Principales métodos:
- Medición de KIEs para varios sustratos de 5-metiltioadenosina (MTA) etiquetados isotópicamente durante la arsenólisis catalizada por MTAP.
- Corrección de KIE para el compromiso a plazo de catálisis para obtener KIE intrínsecos.
- Modelado computacional utilizando DFT para aproximar el estado de transición y compararlo con KIEs experimentales.
Principales resultados:
- Los KIEs intrínsecos primarios (1' - 14C y 9 - 15) N) sugieren un estado de transición disociativo S - N) 1 con un centro catiónico en el carbono anómero y un grupo de salida de adenina aniónica.
- El análisis computacional indica una participación nucleófila significativa del grupo fosfato en el estado de transición, con el nucleófilo de oxígeno posicionado a 2.0 Angstrom del carbono anómero.
- El estado de transición exhibe un carácter zwitteriónico con un carbono anómero catiónico y un oxígeno aniónico 3 '-OH, adoptando una conformación 3 '-endo.
Conclusiones:
- El MTAP humano opera a través de un mecanismo de estado de transición S(N) 1 tardío.
- La participación nucleofílica significativa del grupo fosfato es una característica clave del mecanismo catalítico del MTAP.
- El estudio proporciona una visión estructural y mecanicista detallada de la catálisis de MTAP, valiosa para el diseño de inhibidores.
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