[Catalytic mechanisms and applications of plastic-degrading enzymes: a review]

Enzyme-mediated degradation of plastics is considered as a promising solution for addressing escalating plastic pollution. Extensive studies have identified diverse plastic-degrading enzymes from typical habitats, extreme environments, and different hosts. However, the short co-evolution period between microbes and plastics limits the natural evolution of specific plastic-degrading enzymes. The identified plastic-degrading enzymes mainly belong to the carbohydrate esterase (CE) and auxiliary activity (AA) enzyme families, being involved in lignin degradation. Consequently, lignin degradation-related enzymes represent a promising resource for the discovery of novel plastic-degrading enzymes. The available studies on the catalytic mechanisms and applications of plastic-degrading enzymes mainly focused on IsPETase and leaf-branch compost cutinase (LCC). Systematic insights into non-hydrolytic plastic-degrading enzymes remain scarce. This review summarizes the types and catalytic mechanisms of plastic-degrading enzymes related to C-O and C-C backbone plastics, and advancements in their screening strategies, engineering modifications, and applications over the past five years. These findings contribute to the collaborative evolution of enzyme research in terms of mechanisms and application innovation. Furthermore, this review establishes a theoretical framework for plastic pollution control.