P450-catalyzed polyethylene oligomer degradation: A quantum mechanics/molecular mechanics study

Polyethylene (PE) waste is mainly disposed by landfill and incineration, which causes severe environmental issues. Enzyme technology shows great potential in degrading PE waste. Here, the degradation mechanism of PE oligomer (tetramer) by P450 BM3 variant was systematically explored with the aid of molecular dynamics simulations and quantum mechanics/molecular mechanics calculations. We found that the degradation includes two processes: hydrogen abstraction and rebound. The hydrogen abstraction process was determined as the rate-determining step with the Boltzmann-weight average energy barrier of 14.0 kcal/mol, which generally aligns with the experimental available kinetic data (turnover rate: 3020 min⁻¹). Regio- and stereoselectivity during the degradation process were also revealed. Correlations between 38 key features and energy barriers were screened and key structural parameters that have strong influence on PE degradation efficiency were identified. The degradation process of polyvinyl chloride (PVC) oligomer also includes hydrogen abstraction and rebound step, while the catalytic energy landscape of rebound step is different from PE oligomer. In summary, these new insights provide an environmentally friendly strategy for green and efficient removal of PE an PVC waste.