The effect of ionic strength on PETase enzymes: An experimental and computational study

Area of Science:

• Biocatalysis and enzyme engineering
• Environmental biotechnology
• Polymer science

Background:

• Enzymes degrading polyethylene terephthalate (PET) are crucial for plastic waste management.
• IsPETase exhibits high activity at low temperatures.
• PETaseSM14, a novel enzyme, functions in high-salt conditions, but its properties are poorly understood.

Purpose of the Study:

• To investigate the structural and catalytic differences between IsPETase and PETaseSM14 under varying salt concentrations.
• To understand how ionic strength affects enzyme activity and stability.
• To provide insights for engineering improved PET-degrading enzymes.

Main Methods:

• All-atom molecular dynamics simulations.
• In vitro enzymatic assays.
• Analysis of enzyme behavior across a range of NaCl concentrations (150–900 mM).

Main Results:

• IsPETase's flexible binding site aids substrate binding but leads to instability in high salt.
• PETaseSM14 possesses a smaller, rigid pocket that adapts to increasing salt, enhancing water and substrate recruitment.
• Both enzymes bind PET chains similarly to amorphous PET.

Conclusions:

• Enzyme structure, particularly the binding site, dictates performance under varying ionic strengths.
• PETaseSM14 shows potential for PET degradation in saline environments.
• Structural insights can guide the development of robust enzymes for diverse plastic recycling applications.