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La cicloadición [4+2] catalizada por enzimas es un paso clave en la biosíntesis de la spinosyn A

Hak Joong Kim¹, Mark W Ruszczycky, Sei-hyun Choi

¹Department of Chemistry and Biochemistry, University of Texas at Austin, Austin, Texas 78712, USA.

|May 6, 2011

Resumen

Los investigadores identificaron SpnF, la primera enzima dedicada que cataliza las reacciones de Diels-Alder en la biosíntesis de la espinosina A. Esta enzima acelera específicamente la formación de anillos de ciclohexeno, aclarando un paso clave en la síntesis de productos naturales.

Área de la Ciencia:

La bioquímica es la bioquímica.
Química orgánica es la química orgánica.
Enzimología Enzimología.

Sus antecedentes:

La reacción de Diels-Alder es crucial para la síntesis de productos naturales que contienen ciclohexeno.
La catálisis enzimática de las reacciones de Diels-Alder es rara, con sólo cuatro enzimas implicadas previamente.
Las enzimas existentes a menudo poseen múltiples actividades, oscureciendo su papel específico en la cicloadición.

Objetivo del estudio:

Para investigar la biosíntesis de spinosyn A, un producto natural complejo.
Identificar y caracterizar las enzimas involucradas en la formación de la estructura del núcleo de la espinosina A.
Para determinar si las enzimas específicas catalizan las reacciones de cicloadición de Diels-Alder en esta vía.

Principales métodos:

Estudió la biosíntesis de la espinosina A en la Saccharopolyspora spinosa.
Enzima ciclasa SpnF. identificada y purificada.
Se realizó un análisis cinético para determinar la actividad catalítica de SpnF y la mejora de la velocidad.
Enzima SpnL identificada para el siguiente paso de puente cruzado.

Principales resultados:

Se identificó SpnF como una ciclasa que cataliza una cicloadición [4+2] transanular para el anillo de ciclohexeno de la spinosina A.
SpnF demostró una mejora significativa de la velocidad de 500 veces para esta reacción específica.
Identificó a SpnL como responsable del paso final de puente cruzado, completando el núcleo tetraciclico.
SpnF es la primera enzima autónoma caracterizada dedicada exclusivamente a la catálisis de Diels-Alder.

Conclusiones:

SpnF es la primera enzima caracterizada que cataliza exclusivamente una cicloadición Diels-Alder [4+2] in vitro.
El estudio aclara completamente la formación de la porción de perhidro-como-indaceno en el spinosyn A.
Este trabajo proporciona un ejemplo clave de las reacciones Diels-Alder mediadas por enzimas en la biosíntesis de productos naturales.

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