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La glucosilación del aspartato desencadena la isomerización al isoaspartato
John Janetzko1,2, Suzanne Walker2
1Department of Chemistry and Chemical Biology, Harvard University , Cambridge, Massachusetts 02138, United States.
Journal of the American Chemical Society
|February 17, 2017
Resumen
La enzima β-N-acetilglucosamina transferasa (OGT) vinculada a O glicosila rápidamente los residuos de aspartato, formando un intermediario que conduce a la isomerización de las proteínas. Esto sugiere que la OGT puede catalizar enzimáticamente la conversión de aspartato en isoaspartato en las células.
Área de la Ciencia:
- La bioquímica
- Enzimología
- Biología molecular
Sus antecedentes:
- La O-N-acetilglucosamina transferasa (OGT) es una enzima humana clave involucrada en la glicosilación de las proteínas.
- La OGT media la escisión del factor de célula huésped 1 (HCF-1) a través de la glicosilación inicial de los residuos de glutamato.
- Estudios anteriores indicaron que la sustitución del glutamato por el aspartato en el HCF-1 previene la escisión, pero no se examinó la glicosilación del aspartato.
Objetivo del estudio:
- Investigar la actividad de glicosilación de la OGT en el aspartato en comparación con el glutamato.
- Elucidar el mecanismo de reacción y los productos de la glucosilación del aspartato mediada por OGT.
- Explorar el papel enzimático potencial de la OGT y otras enzimas en la isomerización de aspartato a isoaspartato.
Principales métodos:
- Análisis comparativo de las tasas de glicosilación de la OGT en sustratos de péptidos modelo que contienen glutamato frente al aspartato.
- Caracterización de los productos intermedios y finales de la reacción mediante espectrometría de masas y secuenciación de péptidos.
- En el análisis de silicio y la revisión de la literatura de las posibles enzimas implicadas en la isomerización del aspartato.
Principales resultados:
- OGT exhibe una glicosilación significativamente más rápida del aspartato que el glutamato en los péptidos modelo.
- La glicosilación del aspartato catalizado por OGT se produce a través de un intermediario de succinimida.
- El succinimida intermedio se hidroliza para formar péptidos isoaspartilo, lo que indica una isomerización de aspartato a isoaspartato catalizada por la enzima.
- Las polimerasas poli (ADP-ribosa) (PARP) también se sugieren como catalizadores potenciales para la isomerización del aspartato.
Conclusiones:
- OGT puede glicosilizar el aspartato de manera eficiente, lo que lleva a la formación de péptidos isoaspartilo.
- Este estudio revela una nueva vía enzimática para la isomerización de aspartato a isoaspartato, desafiando la noción de que es exclusivamente no enzimática.
- Los hallazgos implican a los OGT y potencialmente a los PARP en la modificación y reparación de proteínas celulares a través de la isomerización del aspartato.
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