Polyethylene terephthalate (PET) is a widely used synthetic polymer and known to contaminate marine and terrestrial ecosystems. As of today, approximately 100 PET active-enzymes (PETases) are recognized as active candidates for enzymatic degradation of PET, however, most of them only exhibit moderate activity. Therefore, we used our established metagenome-pipeline to identify novel enzymes that show high activity towards polymer degradation. Amongst others, we identified an enzyme affiliated with Alkalilimnicola ehrlichii. U-HPLC measurement of PET degradation products as well as molecular characterization implies that PET44 is a highly promiscuous esterase with the ability to effectively degrade PET, BHET and MHET down to TPA and Ethylene glycol at an optimal temperature of 40°C. It shows high sequence similarity to the IsPETase, (53.6%) and the LCC (46.4 %), two prominent and highly active PETases. Semi-rational protein engineering was used to obtain PET44 modifications similar to those of the most relevant industrial mutants of the IsPETase and the LCC (ThermoPETase, DuraPETase, HotPETase, LCC-ICCG). Our work contributes to better structure-function predictions of PETases and enhances our understanding of the essential features a true active PETase really needs in order to be efficient