Plastics have become the choice material for the manufacture and storage of goods, in part because plastics are cheap, durable, and sterile. However, those same qualities have led to a massive pollution issue over the last several decades. Besides the amount of plastic already present in landfills, there is even more plastic floating in large debris fields in nearly every major ocean on the planet. Recently a bacterium,<i> Ideonella sakaiensis</i> 201-F6, was discovered in a plastics recycling facility that has evolved the ability to consume poly(ethylene terephthalate) (PET) via the enzyme PETase. More recently the crystal structure of PETase was resolved and the binding of PET into PETase determined via computational docking. Here we determined the reaction mechanism of PET degradation by PETase via Quantum Mechanical/Molecular Mechanical methods. We used the aimless shooting approach to transition path sampling to generate reactive trajectories and likelihood maximization to obtain optimal reaction coordinates, essentially elucidating the reaction mechanism. The best reaction coordinate was used to calculate the free energy and rate constant for both acylation and deacylation reaction steps. Additionally, we probed the W159H/S238F double mutant previously shown to exhibit improved PET degradation activity.

Determining the reaction mechanism of a plastic-degrading aromatic polyesterase via transition path sampling

2019 Spring National Meeting

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