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Las interacciones entre carbohidratos y proteínas que impulsan la translocación procesal de polisacáridos en enzimas

Brandon C Knott¹, Michael F Crowley, Michael E Himmel

¹National Bioenergy Center and ‡Biosciences Center, National Renewable Energy Laboratory , Golden, Colorado 80401, United States.

Journal of the American Chemical Society

|May 30, 2014

Resumen

La degradación enzimática de la celulosa implica un mecanismo de roscado de cadena de dos pasos, con la hidrólisis, no la translocación de la cadena, como el paso que limita la velocidad. Las interacciones específicas de proteínas impulsan el movimiento de los polisacáridos a través de las hidrolasas de glucósidos.

Área de la Ciencia:

La bioquímica es la bioquímica.
Biología Estructural Biología estructural.
Enzimología Enzimología.

Sus antecedentes:

La translocación de polisacáridos a través de túneles de proteínas es vital en enzimas como las hidrolasas de glucósidos.
Estudios anteriores se centraron en la unión estática, dejando los detalles moleculares de la procesividad de la cadena de polisacáridos poco claros.

Objetivo del estudio:

Investigar el mecanismo molecular de la translocación de la cadena de celulosa durante el ciclo procesativo de la familia de hidrolasas glicosídicas 7 cellobiohidrolasas.
Para aclarar el papel de las interacciones proteína-carbohidrato en el movimiento de la cadena de polisacáridos y la catálisis enzimática.

Principales métodos:

Se utilizaron simulaciones de dinámica molecular para examinar la translocación de la cadena de celulosa.
Análisis de las barreras de energía libre para el enhebrado de la cadena y la hidrólisis.
Interacciones electrostáticas y aromáticas-carbohidratos investigadas dentro del sitio activo de la enzima.

Principales resultados:

Se identificó un mecanismo de dos pasos para el enhebrado de la cadena para formar un complejo de Michaelis.
La barrera de energía libre para el enhebrado de cadena es sustancialmente más baja que la barrera de hidrólisis.
Las interacciones electrostáticas con los residuos polares conservados impulsan la translocación, mientras que los residuos aromáticos guían la cadena.

Conclusiones:

La degradación enzimática de la celulosa está limitada por la reacción de glicosilación, no por la procesividad en cadena.
Los residuos específicos conservados y las interacciones aromáticas son cruciales para la translocación procesal en las hidrolasas de glucósidos.
Este estudio aclara los motivos comunes en las enzimas activas de carbohidratos que facilitan la síntesis y degradación de los polisacáridos.

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