如果你曾经看过一个细胞的分离实验的动画，你将会欣赏细胞的形状和体积并不是静态的。瑞典Chalmers大学的OWE和其同事研究运用实验和理论证实，细胞形状和体积的动态变换会影响细胞内的生物化学反应速率。他们通过分析在微尺度小泡和纳米管里的放生网络里的酶反应特性证实了这一点，同时也采用了理论计算。


The investigators first showed that in a solitary vesicle, reactions can be turned on/off and tuned by volume changes. The rate of volume change has to overwhelm the overall rate of product formation; the volume resulting from the expansion has to be large enough to dilute the substrate concentration well below the Michaelis–Menten constant KM. Orwar and colleagues extended their calculations to the enzymes involved in the mitochondria’s Krebs cycle, thereby demonstrating that organelles can regulate the rates of enzymatic reactions by shrinking or expanding their volume.
The Chalmers investigators next examined whether a reaction could be initiated or boosted in a network of vesicles and nanotubes—the Golgi–endoplasmic reticulum network would be an example—as the arrangement of the network is manipulated. Orwar and colleagues studied fluorescently labeled alkaline phosphatase as the enzyme and fluorescein diphosphate as the substrate. They showed that the reaction system was extremely sensitive to changes in network topology, with the chemical reactions being initiated or boosted in certain places as a function of vesicle–nanotube connectivity. (Proc. Natl. Acad. Sci. U.S.A. 2008, 105, 4099–4104)