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Hydrophobic Salt-modified Nafion for Enzyme Immobilization and Stabilization
Published on: July 11, 2012
El anillo de piridina de NAD se forma por una reacción pericíclica no enzimática
Keri L Colabroy1, Tadhg P Begley
1Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14850, USA.
Journal of the American Chemical Society
|January 20, 2005
Resumen
Se aclara la biosíntesis del ácido quinolínico a partir del triptófano. La enzima 3-hidroxiantranilato-3,4-dioxigenasa (HAD) abre el anillo, y el intermediario resultante se cicliza a través de un tautómero enol a través de una reacción de electrociclado.
Área de la Ciencia:
- La bioquímica es la bioquímica.
- Química orgánica es la química orgánica.
Sus antecedentes:
- El quinolinato (3), un precursor del NAD, se sintetiza a través de dos vías conocidas.
- Una vía implica el aspartato y el fosfato de dihidroxiacetona.
- La otra vía es una degradación del triptófano en cinco pasos que involucra 3-hidroxiantranilato-3,4-dioxigenasa (HAD).
Objetivo del estudio:
- Para dilucidar el mecanismo de la biosíntesis de quinolinato a partir del triptófano.
- Para investigar el papel de la 3-hidroxiantranilato-3,4-dioxigenasa (HAD) en el paso final.
- Para identificar el mecanismo de ciclización del 2-amino-3-carboximucónico semialdehído (ACMS).
Principales métodos:
- Pruebas enzimáticas para determinar la actividad catalítica de HAD en la ciclización ACMS.
- Análisis espectroscópico para estudiar el isomerismo y la tautomerización de ACMS.
- Estudios de reacciones modelo para sondear el mecanismo de ciclización.
Principales resultados:
- La ciclización de ACMS a quinolinato no es catalizada por el HAD.
- El isómero ACMS más estable en solución es la forma totalmente trans, que se isomeriza a través de su tautómero enol.
- Los estudios de modelos sugieren que la ciclización de ACMS procede a través de su tautómero enol a través de una reacción de electrociclado.
Conclusiones:
- La biosíntesis dependiente del triptófano del ácido quinolínico implica una reacción pericíclica.
- Este hallazgo amplía el repertorio conocido de mecanismos de biosíntesis de productos naturales.
- El estudio aclara los pasos finales en la síntesis de precursores de NAD a partir de triptófano.
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