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Cercosporin-Photocatalyzed [4+1]- and [4+2]-Annulations of Azoalkenes Under Mild Conditions
Published on: July 17, 2020
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Identificación de 7-Deoxy-desulfo-argino-cilindrospermopsin, la pieza que falta en la biosíntesis de la
Annick Méjean1, Olivier Lequin2, Olivier Ploux1,3
1LIED, UMR 8236 CNRS, Université Paris Cité, 75205 Paris Cedex 13, France.
Journal of the American Chemical Society
|August 2, 2022
Resumen
Los investigadores identificaron un nuevo precursor de la cilindrospermopsina, la 7-deoxy-desulfo-argino-cilindrospermopsina, en las cianobacterias. Ellos aclararon su biosíntesis, revelando arginina
Área de la Ciencia:
- Bioquímica y Biología Molecular
- Microbiología ambiental
- Química de los productos naturales
Sus antecedentes:
- La cilindrospermopsina es una cianotoxina significativa producida por las cianobacterias de agua dulce.
- Su vía de biosíntesis involucra múltiples poliquetasas y enzimas de adaptación, comenzando con la arginina y la glicina.
- El origen preciso del anillo de uracilo en la cilindrospermopsina ha sido una pregunta de larga data.
Objetivo del estudio:
- Identificar y caracterizar nuevos intermediarios en la biosíntesis de la cilindrospermopsina.
- Para aclarar el papel de las enzimas específicas, CyrG y CyrH, en la vía.
- Determinar el origen del anillo de uracilo y el paso final de condensación en la producción de cilindrospermopsina.
Principales métodos:
- Espectrometría de masas para la identificación de los metabolitos.
- Espectroscopia de RMN en 1D y 2D para elucidar la estructura de la 7-desoxy-desulfo-argino-cylindrospermopsin.
- Experimentos de incorporación isotópica con argininas etiquetadas.
- Sobreproducción de enzimas en Escherichia coli y purificación.
- Ensayos enzimáticos y análisis cinético de CyrG.
- Análisis bioinformático que incluya alineaciones basadas en la estructura y predicciones de la estructura secundaria para CyrF.
Principales resultados:
- Identificación y determinación estructural de la 7-desoxi-desulfo-argino-cilindrospermopsina.
- Confirmación de que la arginina está completamente incorporada y su fracción de guanidina forma el anillo de uracilo.
- CyrG fue identificado como una hidrolasa dependiente del zinc que convierte la 7-deoxy-desulfo-argino-cylindrospermopsin a 7-deoxy-desulfo-cylindrospermopsin y ornitina.
- CyrF, la poliquetida sintasa final, posee un nuevo dominio similar a la N-acetiltransferasa terminal C propuesto para catalizar la condensación con arginina.
Conclusiones:
- El estudio resuelve la pregunta de larga data con respecto al origen del anillo de uracilo en la cilindrospermopsina.
- Se ha caracterizado un nuevo intermediario biosintético y los pasos enzimáticos que involucran CyrG y CyrF.
- El papel propuesto del dominio único de CyrF representa un mecanismo sin precedentes para la terminación de la policetida sintasa.
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