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Homólisis del enlace sacrificial cobalto-carbono en la coenzima B12 como una estrategia de conservación del cofactor
Gregory C Campanello1, Markus Ruetz1, Greg J Dodge1,2
1Department of Biological Chemistry , University of Michigan , Ann Arbor , Michigan 48109-0600 , United States.
Journal of the American Chemical Society
|October 5, 2018
Resumen
Los investigadores descubrieron una nueva estrategia de retención celular para la vitamina B12 (cobalamina). Cuando las enzimas necesarias están ausentes, la adenosiltransferasa descompone la vitamina B12, previniendo su pérdida y asegurando la disponibilidad del cofactor.
Área de la Ciencia:
- La bioquímica
- Biología molecular
- Biología celular
Sus antecedentes:
- La vitamina B12 (cobalamina) es un cofactor esencial para las enzimas humanas.
- Las vías de tráfico intracelular normalmente entregan B12 a sus formas activas y a las enzimas diana.
- Los mecanismos de retención celular para cofactores reactivos como la B12 son cruciales pero no se comprenden completamente.
Objetivo del estudio:
- Para investigar una estrategia inesperada para la retención celular de la vitamina B12.
- Para aclarar el mecanismo de retención del cofactor cuando las enzimas diana no están disponibles.
- Caracterizar las especies intermedias involucradas en este proceso de retención.
Principales métodos:
- Caracterización espectroscópica de los intermediarios de las reacciones.
- Pruebas de actividad enzimática.
- Análisis de los niveles de vitamina B12 en pacientes con afecciones genéticas específicas.
Principales resultados:
- La adenosiltransferasa cataliza la escisión homolítica del enlace cobalto-carbono en la coenzima B12 cuando la metilmalonil-CoA mutaza está ausente.
- El producto de homólisis resultante se une más fuertemente a la adenosiltransferasa, lo que facilita la retención del cofactor.
- Un intermedio caracterizado espectroscópicamente muestra un enlace de cobalto-carbono debilitado antes de la escisión.
- Se observaron niveles más bajos de la coenzima B12 en pacientes con disfunción de la metilmalonil-CoA mutasa y la adenosiltransferasa normal.
Conclusiones:
- Una nueva actividad catalítica de sacrificio de la adenosiltransferasa asegura la retención celular de vitamina B12.
- Este mecanismo evita la pérdida de cofactor al descomponer la vitamina B12 cuando su vía de utilización está bloqueada.
- Los hallazgos proporcionan nuevos conocimientos sobre el metabolismo de la vitamina B12 y la homeostasis del cofactor.
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