Structural Insights into (Tere)phthalate-Ester Hydrolysis by a Carboxylesterase and Its Role in Promoting PET Depolymerization

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Authors

VON HAUGWITZ Gerlis HAN Xu PFAFF Lara LI Qian WEI Hongli GAO Jian METHLING Karen AO Yufei BRACK Yannik MIČAN Jan FEILER Christian G WEISS Manfred S BEDNÁŘ David PALM Gottfried J. LALK Michael LAMMERS Michael DAMBORSKÝ Jiří WEBER Gert LIU Weidong BORNSCHEUER Uwe T. WEI Ren

Year of publication 2022
Type Article in Periodical
Magazine / Source ACS Catalysis
MU Faculty or unit

Faculty of Science

Citation
Web https://doi.org/10.1021/acscatal.2c03772
Doi http://dx.doi.org/10.1021/acscatal.2c03772
Keywords PET hydrolysis; plastic; dual enzyme system; carboxylesterase; structure; enzyme engineering
Attached files
Description TfCa, a promiscuous carboxylesterase from Thermobifida fusca, was found to hydrolyze polyethylene terephthalate (PET) degradation intermediates such as bis(2-hydroxyethyl) terephthalate (BHET) and mono-(2-hydroxyethyl)-terephthalate (MHET). In this study, we elucidated the structures of TfCa in its apo form, as well as in complex with a PET monomer analogue and with BHET. The structure–function relationship of TfCa was investigated by comparing its hydrolytic activity on various ortho- and para-phthalate esters of different lengths. Structure-guided rational engineering of amino acid residues in the substrate-binding pocket resulted in the TfCa variant I69W/V376A (WA), which showed 2.6-fold and 3.3-fold higher hydrolytic activity on MHET and BHET, respectively, than the wild-type enzyme. TfCa or its WA variant was mixed with a mesophilic PET depolymerizing enzyme variant [Ideonella sakaiensis PETase (IsPETase) PM] to degrade PET substrates of various crystallinity. The dual enzyme system with the wild-type TfCa or its WA variant produced up to 11-fold and 14-fold more terephthalate (TPA) than the single IsPETase PM, respectively. In comparison to the recently published chimeric fusion protein of IsPETase and MHETase, our system requires 10% IsPETase and one-fourth of the reaction time to yield the same amount of TPA under similar PET degradation conditions. Our simple dual enzyme system reveals further advantages in terms of cost-effectiveness and catalytic efficiency since it does not require time-consuming and expensive cross-linking and immobilization approaches.
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