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Difusión mejorada y disociación de enzimas oligoméricas

Ah-Young Jee1, Kuo Chen2,3, Tsvi Tlusty1,4

  • 1Center for Soft and Living Matter , Institute for Basic Science (IBS) , Ulsan 44919 , South Korea.

Journal of the American Chemical Society
|November 29, 2019
PubMed
Resumen
Este resumen es generado por máquina.

Las enzimas oligoméricas como la ureasa pueden disociarse en subunidades de difusión más rápida por encima de las concentraciones de sustrato de la constante de Michaelis (kM). Esta disociación de la subunidad ofrece una explicación física para la difusión de la enzima mejorada en concentraciones más altas.

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Área de la Ciencia:

  • La bioquímica
  • Enzimología
  • La biofísica

Sus antecedentes:

  • Las enzimas oligoméricas se han propuesto como máquinas moleculares que convierten la energía química en movimiento.
  • En estudios previos sobre el aumento de la difusión enzimática a menudo se utilizaron concentraciones de sustrato superiores a la relevancia biológica (por encima de kM).

Objetivo del estudio:

  • Investigar el mecanismo de la difusión aumentada en las enzimas oligoméricas, en particular la ureasa.
  • Determinar si la disociación de la enzima en subunidades contribuye a una mayor difusión a concentraciones en el sustrato superiores a la constante de Michaelis (kM).

Principales métodos:

  • Se utilizaron cuatro técnicas analíticas independientes: dispersión estática de la luz, dispersión dinámica de la luz (DLS), cromatografía de exclusión de tamaño (SEC) y espectroscopia de correlación de fluorescencia (FCS).
  • Se examinó el comportamiento de la enzima en diferentes concentraciones de sustrato, centrándose en las condiciones por encima y por debajo de la constante de Michaelis (kM).

Principales resultados:

  • Se ha demostrado que la ureasa y otras enzimas oligoméricas (hexoquinasa, acetilcolinesterasa, aldolasa) se disocian en subunidades a concentraciones de sustrato superiores a kM.
  • Se observó una difusión significativamente mejorada para estas enzimas solo cuando se disociaron en subunidades.
  • Se encontró hasta un aumento del 10% en el coeficiente de difusión para la ureasa y la acetilcolinesterasa por debajo de kM donde no se produjo la disociación, en consonancia con las predicciones teóricas.

Conclusiones:

  • La disociación de las subunidades enzimáticas por encima de kM proporciona un mecanismo físico simple para una mayor difusión.
  • La difusión mejorada de las enzimas oligoméricas es impulsada principalmente por la disociación de las subunidades a concentraciones supra-Michaelis.
  • Los hallazgos concilian las observaciones experimentales con los modelos teóricos de cinética y difusión de las enzimas.