2020 Conference Objects and Presentations (Communicative Events)

Enhanced Diffusion of Catalytically Active Enzymes

Zhang, Yifei; Hess, Henry S.

The past decade has seen an increasing number of investigations into enhanced diffusion of catalytically active enzymes [1]. These studies suggested that enzymes are actively propelled as they catalyze reactions or bind with ligands (e.g., substrates or inhibitors). In this Outlook, we chronologically summarize and discuss the experimental observations and theoretical interpretations and emphasize the potential contradictions in these efforts. We point out that the existing multimeric forms of enzymes or isozymes may cause artifacts in measurements and that the conformational changes upon substrate binding are usually not sufficient to give rise to a diffusion enhancement greater than 30%. Therefore, more rigorous experiments and a more comprehensive theory are urgently needed to quantitatively validate and describe the enhanced enzyme diffusion.

We utilized dynamic light scattering (DLS) to measure the diffusion coefficient of aldolase in the absence and presence of its substrate [2]. The DLS measurements have an experimental error of 3% and do not find a statistically significant change of the aldolase diffusion coefficient even at a saturating substrate concentration. This finding lends support to the contention that photophysical artifacts may have affected the prior FCS measurements and challenges the idea that enzymes can be self-propelled by their catalytic activity.