Involved in the degradation and assimilation of the plastic poly(ethylene terephthalate) (PET), which allows I.sakaiensis to use PET as its major energy and carbon source for growth. Likely acts synergistically with PETase to depolymerize PET. Catalyzes the hydrolysis of mono(2-hydroxyethyl) terephthalate (MHET) into its two environmentally benign monomers, terephthalate and ethylene glycol. Does not show activity against PET, bis(hydroxyethyl) terephthalate (BHET), pNP-aliphatic esters or typical aromatic ester compounds catalyzed by the tannase family enzymes, such as ethyl gallate and ethyl ferulate. 4-[(2-hydroxyethoxy)carbonyl]benzoate + H2O = ethylene glycol + H(+) + terephthalate kcat is 31 sec(-1) for the hydrolysis of mono(2-hydroxyethyl) terephthalate (at pH 7 and 30 degrees Celsius). Highly up-regulated during growth on PET film. Has potential for application in environmental remediation and biological recycling of PET waste products. The calcium ion is located far from the active site and appears to have a role in stabilization of the lid domain. Belongs to the tannase family. Of plastic and men - Issue 181 of July 2016