Plastic-Eating Enzymes Decoded—PETase’s Structure and Mutation Map

  • PETase’s catalytic triad and binding pocket facilitate PET breakdown.
  • Strategic mutations radically boost PETase’s activity and thermostability.
  • Structural remodeling increases substrate access and enzyme resilience.
  • Machine learning accelerates discovery of optimal PETase variants.
  • Enhanced PETase holds promise for treating microplastics in humans.
  1. Current advances in the structural biology and molecular engineering of PETase (2023)
  2. Degradation of PET microplastic particles to monomers in human serum by PETase (2024)
  3. FAST-PETase hydrolysis enhancement (2023)
  4. HotPETase directed evolution (2022)
  5. Double mutation impacts on PETase (2023)

The crisis of microplastics in the environment and the human body has propelled scientific interest toward PETase, the enzyme from Ideonella sakaiensis renowned for its ability to break down poly(ethylene terephthalate) (PET). PETase’s alpha/beta hydrolase fold positions a catalytic triad—serine, histidine, and aspartate—to attack PET’s stubborn ester bonds. While PETase’s native form operates at low efficiency, breakthroughs in protein engineering have produced mutants that are both more active and more stable. Key advances include FAST-PETase, carrying multiple mutations (S121E, D186H, R224Q, N233K, R280A), DuraPETase with eleven substitutions, and HotPETase, which has 21 modifications. These mutations enhance catalytic activity by optimizing substrate binding, introducing hydrogen bonds, and re-engineering the enzyme’s active site geometry.

Table 2 from Liu et al. details dramatic increases in optimal temperature (e.g., DuraPETase from 46.8°C to 77°C) and hydrolysis rates. Structural studies reveal that altered loops and surface charges allow easier access to PET, and some changes create new allosteric regulation routes—for example, new electrostatic interactions and “aromatic tunnels” improve affinity for PET’s aromatic motif. This fine-tuning enables PETase to operate effectively against both amorphous and crystalline microplastics, a critical requirement for biomedical applications.

With computational and machine learning techniques now guiding mutation selection, enzyme variants are engineered for maximal depolymerization of PET even in challenging biological conditions. Such powerful mutants pave the way for future biotherapeutics, aiming to clear microplastics from human blood and tissues.