Department of Biomedical Engineering, Columbia University, New York, New York 10027, USA.
Nat Commun. 2016 Dec 22;7:13982. doi: 10.1038/ncomms13982.
A proximity effect has been invoked to explain the enhanced activity of enzyme cascades on DNA scaffolds. Using the cascade reaction carried out by glucose oxidase and horseradish peroxidase as a model system, here we study the kinetics of the cascade reaction when the enzymes are free in solution, when they are conjugated to each other and when a competing enzyme is present. No proximity effect is found, which is in agreement with models predicting that the rapidly diffusing hydrogen peroxide intermediate is well mixed. We suggest that the reason for the activity enhancement of enzymes localized by DNA scaffolds is that the pH near the surface of the negatively charged DNA nanostructures is lower than that in the bulk solution, creating a more optimal pH environment for the anchored enzymes. Our findings challenge the notion of a proximity effect and provide new insights into the role of DNA scaffolds.
一种临近效应被用来解释酶级联在 DNA 支架上的活性增强。在这里，我们使用葡萄糖氧化酶和辣根过氧化物酶进行的级联反应作为模型系统，研究了在酶游离于溶液中、彼此连接以及存在竞争酶时的级联反应动力学。没有发现临近效应，这与预测快速扩散的过氧化氢中间物充分混合的模型一致。我们认为，通过 DNA 支架定位的酶的活性增强的原因是带负电荷的 DNA 纳米结构表面附近的 pH 值低于溶液中的 pH 值，为固定化酶创造了更理想的 pH 值环境。我们的发现挑战了临近效应的概念，并为 DNA 支架的作用提供了新的见解。
