Enzymes as Active Matter

Nature has designed multifaceted cellular structures to support life. Cells contain a vast array of enzymes that collectively perform essential tasks by harnessing energy from chemical reactions. Despite the complexity, intra- and intercellular motility at low Reynolds numbers remain the epicenter of life. In the past decade, detailed investigations on enzymes that are freely dispersed in solution have revealed concentration-dependent enhanced diffusion and chemotactic behavior during catalysis. Theoretical calculations and simulations have determined the magnitude of the impulsive force per turnover; however, an unequivocal consensus regarding the mechanism of enhanced diffusion has not been reached. Furthermore, this mechanical force can be transferred from the active enzymes to inert particles or surrounding fluid, thereby providing a platform for the design of biomimetic systems. Understanding the factors governing enzyme motion would help us to understand organization principles for dissipative self-assembly and the fabrication of molecular machines. The purpose of this article is to review the different classes of enzyme motility and discuss the possible mechanisms as gleaned from experimental observations and theoretical modeling. Finally, we focus on the relevance of enzyme motion in biology and its role in future applications.