Effect of macromolecular crowding on the rate of diffusion-limited enzymatic reaction

TL;DR

This paper investigates how macromolecular crowding in cellular cytoplasm affects molecular diffusion and enzymatic reaction rates, using a numerical model based on percolation theory to explain experimental observations.

Contribution

It introduces a simple numerical model that links macromolecular crowding to diffusion and enzymatic reaction rates in cells, providing qualitative explanations for experimental data.

Findings

Diffusivity decreases with increased crowding.

Enzymatic reaction rates are affected by crowding.

The model qualitatively matches experimental observations.

Abstract

The cytoplasm of a living cell is crowded with several macromolecules of different shapes and sizes. Molecular diffusion in such a medium becomes anomalous due to the presence of macromolecules and diffusivity is expected to decrease with increase in macromolecular crowding. Moreover, many cellular processes are dependent on molecular diffusion in the cell cytosol. The enzymatic reaction rate has been shown to be affected by the presence of such macromolecules. A simple numerical model is proposed here based on percolation and diffusion in disordered systems to study the effect of macromolecular crowding on the enzymatic reaction rates. The model explains qualitatively some of the experimental observations.