Biochemical properties
Our literature searches identified a total of 34 enzymes that have been shown to catalyse the partial degradation of PET to oligomers or even to monomers, originating from four different bacterial phyla and one eukaryotic lineage (Table 1 ). No archaeal PETases have been functionally verified to date.
Many of the currently known PETases are thermostable enzymes, because the catalytic activity increases at temperatures close to the glass transition temperature (65 °C) of PET due to the formation of flexible and thus enzyme-accessible amorphous domains 28. Notably, few enzymes are active at lower temperatures implying they may play a role in cold-adapted PET degradation 29. However, all known native PETases have rather low catalytic activity toward PET.