Structure of plastic-munching enzyme MHETase solved

Plastic bottles and packaging made from poly(ethylene terephthalate) (PET) are ubiquitous, and plastic litter is a global problem, from the great Pacific garbage patch to the air we breathe. PET can be broken down and reused, but the process is not widely employed. In 2016, researchers discovered a bacterium that partially feeds on PET. The bacterium uses two enzymes: PETase converts PET to mono(2-hydroxyethyl) terephthalate (MHET) and then MHETase breaks that product into terephthalic acid and ethylene glycol. Researchers at the University of Greifswald and Helmholtz-Zentrum Berlin have now solved the crystal structure of MHETase (Nat. Commun. 2019, DOI: 10.1038/s41467-019-09326-3), showing how the enzyme closes around the substrate when it docks. After determining the active-site structure, the team made mutants that work at higher substrate concentrations and can break down another substrate, taking another step in the journey toward plastics biorecycling.