Kinetics of diffusion-influenced multisite phosphorylation with enzyme reactivation.

Area of Science:

• Biochemistry
• Chemical Kinetics
• Enzyme Kinetics

Background:

• Multisite phosphorylation kinetics are complex and influenced by diffusion.
• Conventional rate equations may not fully capture diffusion effects.
• Enzyme inactivation and reactivation add further complexity.

Purpose of the Study:

• To extend diffusion-modified kinetic models to include enzyme reactivation.
• To develop a more accurate theoretical framework for short-time kinetics.
• To investigate the impact of enzyme reactivation on phosphorylation cycles.

Main Methods:

• Modification of conventional rate equations to include diffusion.
• Introduction of new transitions and enzyme reactivation steps.
• Development of a non-Markovian theory with memory kernels.
• Application to double phosphorylation and phosphorylation-dephosphorylation cycles.

Main Results:

• A diffusion-modified kinetic scheme with a negative rate constant emerged due to enzyme reactivation.
• Non-Markovian effects are significant at short times.
• The non-Markovian theory accurately describes short-time kinetics.
• Loss of bistability in a phosphorylation-dephosphorylation cycle was reproduced with decreasing enzyme reactivation time.

Conclusions:

• Enzyme reactivation significantly alters diffusion-influenced phosphorylation kinetics.
• A non-Markovian approach is essential for accurate modeling at short timescales.
• The developed theory provides a more robust framework for understanding complex enzymatic reactions.