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Arquitectura enzimática: erección de la orotidina activa 5'- monofosfato descarboxilasa por cambios conformacionales

Archie C Reyes¹, Tina L Amyes¹, John P Richard¹

¹Department of Chemistry, University at Buffalo, SUNY , Buffalo, New York 14260-3000, United States.

Journal of the American Chemical Society

|October 24, 2017

Resumen

La orotidina 5'- monofosfato descarboxilasa (OMPDC) estabiliza los estados de transición a través de cambios conformacionales inducidos por el sustrato. Este mecanismo enzimático, que involucra fragmentos de sustrato, puede conducir a la activación de la enzima.

Área de la Ciencia:

La bioquímica
Cinética de las enzimas
Biología estructural

Sus antecedentes:

La orotidina 5 extquotesingle- monofosfato descarboxilasa (OMPDC) es una enzima clave en la biosíntesis de la pirimidina.
La comprensión de los mecanismos enzimáticos, particularmente la estabilización del estado de transición, es crucial para el desarrollo de fármacos.

Objetivo del estudio:

Investigar el mecanismo catalítico de la OMPDC, centrándose en la estabilización del estado de transición.
Para aclarar el papel de la unión de sustratos y cambios en la conformación de la enzima en la catálisis.

Principales métodos:

Estudios de cinética enzimática con OMPDC y su sustrato 5-fluoroorotato (FO).
Análisis de los parámetros cinéticos (kcat/Km) y de las energías de estabilización del estado de transición.
Se han investigado las contribuciones de estabilización de los fragmentos de sustrato (fosfodianio, ribosilo, anillos de orotato) y los efectores (fosfito dianio, d-glicerol 3-fosfato, d-eritritol 4-fosfato).

Principales resultados:

OMPDC estabiliza el estado de transición para la descarboxilación de OMP en 31 kcal/mol.
Las contribuciones específicas a la estabilización se cuantificaron para el fosfodianión (11,8 kcal/mol), el anillo de ribosilo (10,6 kcal/mol) y el anillo de orotato (8,6 kcal/mol).
El estado de transición para la descarboxilación de FO se estabiliza en 5,2, 7,2 y 9,0 kcal/mol con fosfito dianio, d-glicerol 3-fosfato y d-eritritol 4-fosfato, respectivamente.
La unión del fragmento de sustrato impulsa un cambio de conformación de la enzima, formando un complejo enjaulado.

Conclusiones:

OMPDC utiliza cambios conformacionales inducidos por el sustrato para la catálisis, estabilizando el estado de transición.
Las interacciones de unión de los fragmentos de sustrato son críticas para bloquear el anillo orotado en una conformación catalíticamente competente.
La activación enzimática puede ser una consecuencia de estos cambios conformacionales inducidos por el sustrato.

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