(84f) A Theory of Enzyme Chemotaxis: Comparison between Experiment and Model

Enzymes show two distinctive transport behaviors in the presence of their substrate in solution. Their diffusivity enhances as substrate concentration increases. Also, enzymes perform directional movement toward high substrate concentration which is called chemotaxis. A variety of enzymes has been studied in the past few years but there is still a lack of general understanding of enzyme chemotaxis. In this study, we provide a general expression for the active movement of an enzyme in the concentration gradient of its substrate. The proposed model takes into account both the substrate-binding and catalytic turnover step. It uses the Michaelis-Menten kinetic parameters of an enzyme to predict the active movement of it. We have experimentally measured the chemotaxis level of two different enzymes, urease and hexokinase, under various conditions. The experimental values of chemotaxis have been compared with the results from the available theories to explore the level of agreement. We found that the existing theories significantly overestimate or underestimate the active movement of the studied enzymes. However, our proposed model is in agreement with the experimental results.