1. Analysis of Poly(ethylene terephthalate) degradation kinetics of evolved IsPETase variants using a surface crowding model.
- Author
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Zhong-Johnson, En Ze Linda, Ziyue Dong, Canova, Christopher T., Destro, Francesco, Cañellas, Marina, Hoffman, Mikaila C., Maréchal, Jeanne, Johnson, Timothy M., Zheng, Maya, Schlau-Cohen, Gabriela S., Lucas, Maria Fátima, Braatz, Richard D., Sprenger, Kayla G., Voigt, Christopher A., and Sinskey, Anthony J.
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BIOCHEMICAL models , *MOLECULAR dynamics , *COLLECTIVE behavior , *ETHYLENE , *FLUORESCENCE microscopy , *CRYSTALLIZATION , *PET supplies - Abstract
Poly(ethylene terephthalate) (PET) is a major plastic polymer utilized in the single-use and textile industries. The discovery of PET-degrading enzymes (PETases) has led to an increased interest in the biological recycling of PET in addition to mechanical recycling. IsPETase from Ideonella sakaiensis is a candidate catalyst, but little is understood about its structurefunction relationships with regards to PET degradation. To understand the effects of mutations on IsPETase productivity, we develop a directed evolution assay to identify mutations beneficial to PET film degradation at 30 °C. IsPETase also displays enzyme concentration-dependent inhibition effects, and surface crowding has been proposed as a causal phenomenon. Based on total internal reflectance fluorescence microscopy and adsorption experiments, IsPETase is likely experiencing crowded conditions on PET films. Molecular dynamics simulations of IsPETase variants reveal a decrease in active site flexibility in free enzymes and reduced probability of productive active site formation in substrate-bound enzymes under crowding. Hence, we develop a surface crowding model to analyze the biochemical effects of three hit mutations (T116P, S238N, S290P) that enhanced ambient temperature activity and/or thermostability. We find that T116P decreases susceptibility to crowding, resulting in higher PET degradation product accumulation despite no change in intrinsic catalytic rate. In conclusion, we show that a macromolecular crowdingbased biochemical model can be used to analyze the effects of mutations on properties of PETases and that crowding behavior is a major property to be targeted for enzyme engineering for improved PET degradation. [ABSTRACT FROM AUTHOR]
- Published
- 2024
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