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Monitoring the Reductive and Oxidative Half-Reactions of a Flavin-Dependent Monooxygenase using Stopped-Flow Spectrophotometry
Published on: March 18, 2012
Caracterización del radical aniónico de flavina unido covalentemente en la monoamina oxidasa a por la resonancia
Christopher W M Kay1, Hassane El Mkami, Gianluca Molla
1Department of Biology, University College London, UK. c.kay@ucl.ac.uk
Journal of the American Chemical Society
|November 30, 2007
Resumen
Las enzimas monoaminooxidasa (MAO) A y B contienen radicales de flavinas aniónicas, no radicales de tirosilo. MAO A A MAO es el nombre de un libro.
Área de la Ciencia:
- La bioquímica es la bioquímica.
- Enzimología Enzimología.
- La espectroscopia es una técnica de espectroscopia.
Sus antecedentes:
- Existen informes contradictorios con respecto a las especies radicales presentes en la monoamina oxidasa parcialmente reducida (MAO) A.
- Estudios anteriores sugirieron que la MAO A contiene tanto flavina aniónica como radicales tirosílicos, mientras que la MAO B solo mostró un radical de flavina aniónica.
- Se propuso un mecanismo radical revisado para la MAO basado en los hallazgos de la MAO A.
Objetivo del estudio:
- Para resolver la discrepancia en las especies radicales reportadas en MAO A.
- Para investigar la forma radical de MAO A utilizando la resonancia paramagnética de electrones de alta frecuencia (EPR).
- Para comparar las especies radicales y las estructuras electrónicas de MAO A con la d-aminoácida oxidasa (DAAO).
Principales métodos:
- La resonancia paramagnética de electrones de onda continua (EPR) a 94 GHz (banda W) se utilizó para estudiar el MAO A.
- Se registraron espectros de doble resonancia electronuclear pulsada (ENDOR) a 9 GHz (banda X) para MAO A y DAAO.
- Se realizaron cálculos de la teoría funcional de la densidad (DFT) para analizar los patrones de acoplamiento hiperfino.
Principales resultados:
- Se descubrió que tanto la MAO A como la DAAO contienen solo radicales de flavina aniónicos.
- Se observaron distintos patrones de acoplamiento hiperfino entre las flavinas MAO A y DAAO, explicados por diferencias en la posición C8alpha.
- La MAO A tiene una flavina unida covalentemente a la cisteína en C8alfa, mientras que la DAAO tiene una flavina no unida covalentemente.
Conclusiones:
- La presencia de un radical tirosílico en la MAO A no fue apoyada por este estudio.
- Las diferencias en la unión de la flavina en C8alpha influyen en los espectros de EPR observados.
- Se propone un mecanismo de transferencia de hidruro directo, similar al de DAAO, para la catálisis de MAO.
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