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Estabilización de un complejo modelo de hemo-HNO utilizando una porfirina de cerca de bis-piquete voluminosa y

Elizabeth C Manickas¹, Ashley B LaLonde¹, Michael Y Hu²

¹Department of Chemistry and Department of Biophysics, The University of Michigan, Ann Arbor, Michigan 48109-1055, United States.

Journal of the American Chemical Society

|October 12, 2023

Resumen

Los investigadores crearon un complejo modelo de hemo-nitroxilo (HNO) estable, proporcionando la primera caracterización vibratoria y demostrando su papel en la reducción del óxido nítrico (NO) a N2O por el citocromo P450nor.

Área de la Ciencia:

Química bioorgánica
Enzimología
Metabolismo del nitrógeno

Sus antecedentes:

El nitroxilo (HNO), la forma reducida del óxido nítrico (NO), juega un papel en la señalización de los mamíferos y el ciclo del nitrógeno.
El citocromo P450nor (Cyt P450nor) es una enzima hemo que reduce el NO a N2O durante la desnitrificación por hongos.
Se propone que un intermediario clave en Cyt P450nor, el "intermediario I", sea una especie inestable de hemo-HNO, lo que dificulta un estudio detallado.

Objetivo del estudio:

Sintetizar y caracterizar el primer complejo modelo estable de hemo-nitroxilo (HNO).
Elucidar la estructura electrónica y las propiedades vibratorias de los aductos de hemo-HNO.
Investigar la capacidad catalítica de los intermediarios de hemo-HNO en la reducción de NO.

Principales métodos:

Síntesis de un complejo modelo estable de hemo-HNO, [Fe(3,5-Me-BAFP) ((MI) ((NHO) ], utilizando una porfirina de cerco bis-picket de gran tamaño.
El aislamiento y la caracterización espectroscópica completa, incluida la espectroscopia de vibración por resonancia nuclear (NRVS) y el infrarrojo (IR).
Estudios de reactividad con óxido nítrico (NO) para evaluar la formación de N2O.

Principales resultados:

Se sintetizó y caracterizó con éxito un complejo hemo-HNO estable, [Fe(3,5-Me-BAFP) ((MI) ((NHO) ].
La primera caracterización vibratoria completa de un complejo hemo-HNO se logró utilizando IR y NRVS.
Los estudios de reactividad mostraron un alto rendimiento (91 ± 10%) de formación de N2O a partir del complejo hemo-HNO tras la reacción con NO.

Conclusiones:

Los complejos hemo-HNO, modelados por [Fe(3,5-Me-BAFP) ((MI) ((NHO)) ], son estables y pueden ser tratados espectroscópicamente.
Estos hallazgos proporcionan la primera evidencia directa de que los complejos de hemo-HNO son intermediarios catalíticamente competentes en la reducción de NO a N2O mediada por Cyt P450.
El estudio ofrece información crucial sobre el mecanismo de desnitrificación por hongos y el papel más amplio del HNO en la bioquímica del hemo.

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