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Complejo organometálico formado por una enzima radical no convencional de S-adenosilmetionina

Min Dong¹, Masaki Horitani², Boris Dzikovski¹

¹Department of Chemistry and Chemical Biology, Cornell University , Ithaca, New York 14853, United States.

Journal of the American Chemical Society

|July 29, 2016

Resumen

La enzima Pyrococcus horikoshii Dph2 divide un nuevo análogo, revelando un complejo organometálico único. Este descubrimiento avanza en la comprensión de los mecanismos de la enzima radical S-adenosilmetionina y la reactividad del grupo de hierro-azufre.

Área de la Ciencia:

La bioquímica
Enzimología
Biología estructural

Sus antecedentes:

Pyrococcus horikoshii Dph2 (PhDph2) es una enzima radical de la S-adenosilmetionina (SAM, por sus siglas en inglés).
Desempeña un papel crucial en el paso inicial de la biosíntesis de la diftamida.
PhDph2 cataliza la escisión de SAM para formar un radical 3-amino-3-carboxipropilo (ACP).

Objetivo del estudio:

Para investigar el mecanismo de reacción de PhDph2.
Para aclarar la naturaleza de las especies paramagnéticas formadas durante la escisión analógica de SAM.
Comprender la interacción entre el grupo [4Fe-4S] de la enzima y los productos de reacción.

Principales métodos:

Síntesis de un nuevo análogo de SAM (SAMCA) con un grupo 3-carboxialilo.
Escisión enzimática del SAMCA por el PhDph2.
Espectroscopia de doble resonancia de electrones y núcleos (ENDOR) utilizando SAMCA etiquetado isotópicamente.

Principales resultados:

PhDph2 se dividió en SAMCA, generando una especie paramagnética (S = 1/2).
Esta especie fue identificada como un complejo entre el ácido α-sulfinil-3-butenoico y el grupo [4Fe-4S].
Los datos de ENDOR confirmaron un complejo π entre el alqueno y el hierro único del racimo [4Fe-4S].

Conclusiones:

Este estudio presenta el primer ejemplo de un racimo [4Fe-4S] relacionado con SAM que forma un complejo organometálico con un alqueno.
Los hallazgos proporcionan nuevos conocimientos sobre el mecanismo catalítico de PhDph2.
Los resultados amplían los patrones de reactividad conocidos de los grupos [4Fe-4S] en las enzimas SAM radicales.

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