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Perspectivas evolutivas y mecanicistas de la reconstrucción de las sintasas α-humuleno a partir de una moderna (+)
Veronica Gonzalez1, Sabrina Touchet, Daniel J Grundy
1School of Chemistry and ‡Cardiff Catalysis Institute, School of Chemistry, Cardiff University , Main Building, Park Place, Cardiff CF10 3AT, United Kingdom.
Journal of the American Chemical Society
|September 18, 2014
Resumen
Se investigó la actividad de la Germacrene A sintasa (GAS) mediante la alteración de los residuos en el sitio activo. El reemplazo de la glicina 402 en GAS y la glicina 404 en GDS reveló vías evolutivas para las sintasas de sesquiterpenos.
Área de la Ciencia:
- La bioquímica es la bioquímica.
- Enzimología Enzimología.
- Química orgánica es la química orgánica.
Sus antecedentes:
- Las sintasas de sesquiterpenos (SPS) son enzimas cruciales en el metabolismo secundario de las plantas.
- La sintetasa Germacreno A (GAS) de Solidago canadensis generalmente produce (+) -germacreno A a través de la 1,10-ciclización.
- Un producto menor, el α-humuleno, surge de la 1,11-ciclización, lo que sugiere un potencial de doble actividad.
Objetivo del estudio:
- Investigar la base estructural y mecanicista para la selectividad de 1,10-contra 1,11-ciclización en GAS.
- Para explorar la relación evolutiva entre las 1,10- y 1,11-sesquiterpeno sintasas.
- Comprender el papel de los residuos específicos del sitio activo en el control de las vías de ciclización.
Principales métodos:
- Alineaciones de secuencias de aminoácidos de las 1,10 y 1,11-sintasas.
- Cristalografía de rayos X y modelado de homología de GAS.
- Mutagénesis dirigida al sitio de GAS (Gly402) y GDS (Gly404).
- Estudios mecanicistas utilizando etiquetado isotópico de difosfato de farnesilo (FDP) y etiquetado de deuterio.
Principales resultados:
- Identificación de una tríada Thr401-Gly402-Gly403 en el GAS potencialmente responsable de la 1,10-ciclización.
- La mutagenesis de Gly402 en GAS aumentó progresivamente la actividad de 1,11-ciclización.
- La mutagenesis de Gly404 en GDS produjo biciclogermacreno, lo que indica una doble 1,10-/1,11-ciclización.
- Los estudios mecánicos apoyaron un reordenamiento germacreno-humuleno que vinculaba las vías.
Conclusiones:
- Gly402 actúa como un interruptor funcional que controla la 1,10-contra 1,11-ciclización en el GAS.
- Las enzimas con funcionalidades estrictas pueden evolucionar de antepasados menos específicos a través de sustituciones menores.
- Las vías de reacción de los germacrenos y los humulenos están potencialmente vinculadas a través de un intermediario común.
- Las modernas 1,10-sintasas pueden haber evolucionado a partir de las promiscuas 1,11-sesquiterpeno-sintasas.
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