# Substrate Exclusion Greenlights Physical Autocatalysis of Enzyme Activity in Membraneless Proto-Organelles

## TL;DR

This paper shows how membraneless cell structures can boost enzyme activity by controlling their movement and environment.

## Contribution

The study introduces a model system showing how substrate-excluding organelles enhance enzyme activity through physical properties.

## Key findings

- Substrate-excluding organelles increase dextranase mobility and hydrolysis in viscous environments.
- Catalytic enhancement is driven by organelle material properties, not enzyme or substrate concentration.
- Enzyme diffusion in polymer solutions mimics intracellular conditions and highlights catalytic advantages.

## Abstract

Cells modulate phase separation to control condensate
formation,
yet how such organelles affect enzyme activity is poorly understood.
This paper describes how substrate-excluding, membraneless proto-organelles
can increase enzyme mobility while also controlling the extent of
reaction acceleration. The model systeman equimolar polyelectrolyte-nucleotide
coacervateallows for probing compositional influence on the
activity of the biopolymer-processing enzyme dextranase. Increasing
the phase-forming constituent concentrations is sufficient to sustain
fast intradroplet dextranase mobility and enhance hydrolysis, even
when placed in highly viscous, concentrated regimes of the organelle-excluded
substrate dextran. This catalytic uptick is mediated largely by organelle
material properties, eschewing the need for effective substrate or
enzyme concentration enrichment. Physical analysis reveals that dextranase
dimensions fall within the organelle mesh size range and that constituent
concentrations induce changes in droplet viscosity. Enzyme diffusion
measurements within polymer solutions that mimic the intracellular/prebiotic
landscape underscore the catalytic, and potentially evolutionary,
advantage of compartments, enabling faster enzyme mobility.