Effective reaction rates in diffusion-limited phosphorylation-dephosphorylation cycles
Paulina Szymańska1, Marek Kochańczyk2, Jacek Miękisz3
1College of Inter-Faculty Individual Studies in Mathematics and Natural Sciences, University of Warsaw, 02-089 Warsaw, Poland.
Summary
This study reveals how enzyme diffusion impacts biological phosphorylation-dephosphorylation cycles. Lower diffusion rates and molecular crowding affect reaction speeds and substrate states, particularly for less abundant enzymes.
Area of Science:
- Biochemistry
- Biophysics
- Computational Biology
Background:
- Phosphorylation and dephosphorylation are crucial regulatory processes on cell membranes.
- Understanding the kinetics of these opposing enzyme reactions is vital for biological regulation.
Purpose of the Study:
- To investigate the kinetics of membrane-bound phosphorylation-dephosphorylation cycles.
- To determine how diffusion coefficients and enzyme concentrations affect reaction rates and steady-state substrate phosphorylation.
Main Methods:
- Kinetic Monte Carlo simulations on a triangular lattice.
- Analysis of effective macroscopic reaction rate coefficients.
- Examination of steady-state phosphorylated substrate fraction.
Main Results:
- Effective reaction rates and steady-state substrate phosphorylation depend on diffusion and enzyme concentrations.
- Zero-diffusion limit shows reactions only occur between adjacent molecules.
- Nonzero diffusion introduces a linear dependence on diffusion coefficient, creating enzyme-associated substrate clouds and lowering effective rates.
- Molecular crowding influences steady states by altering effective diffusion.
Conclusions:
- Diffusion is a critical factor influencing the kinetics of phosphorylation-dephosphorylation cycles.
- Enzyme abundance and molecular crowding significantly modulate reaction outcomes and steady-state distributions.
- Simulation results align with analytical predictions in limiting diffusion cases.
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