Ahumada Manuel, Calderón Cristian, León Luis, Lissi Eduardo
Facultad de Química y Biología, Universidad de Santiago de Chile, USACH, Santiago, Chile.
Biophys Rev. 2014 Mar;6(1):161-167. doi: 10.1007/s12551-013-0136-9. Epub 2014 Feb 11.
There are numerous studies on systems comprising an enzyme encapsulated in unilamellar liposomes and its substrate initially present in the external aqueous media. Most of these studies are focused on enzyme stability and activity in a restricted media. However, the rate of the process is also determined by the capacity of the substrate to permeate towards the liposome inner pool. In spite of this, there are few studies aimed at a quantitative evaluation of the substrate permeation rate and its lifetime inside the liposome pool. In the present work, we describe, in terms of a very simple mechanism, the permeation of glucose and hydrogen peroxide in DPPC unilamellar liposomes. To this aim, we evaluated the rate of the process employing encapsulated glucose oxidase and catalase in the kinetic diffusion controlled limit. Under this condition, the rate of the process becomes zero order in the enzyme and allows a direct evaluation of the rate constant for the permeation process and the lifetime of a substrate molecule incorporated into the liposome inner pool.
有许多关于由包裹在单层脂质体中的酶及其最初存在于外部水相介质中的底物组成的体系的研究。这些研究大多集中在受限介质中酶的稳定性和活性上。然而，该过程的速率还取决于底物向脂质体内池渗透的能力。尽管如此，旨在定量评估底物渗透速率及其在脂质体池内寿命的研究却很少。在本工作中，我们用一种非常简单的机制描述了葡萄糖和过氧化氢在二棕榈酰磷脂酰胆碱（DPPC）单层脂质体中的渗透。为此，我们在动力学扩散控制极限下，使用包裹的葡萄糖氧化酶和过氧化氢酶评估了该过程的速率。在这种条件下，该过程的速率在酶方面变为零级，并允许直接评估渗透过程的速率常数以及掺入脂质体内池的底物分子的寿命。
