Abstract
Plastics, including poly(ethylene terephthalate) (PET), possess many desirable characteristics and thus are widely used in daily life. However, non-biodegradability, once thought to be an advantage offered by plastics, is causing major environmental problem. Recently, a PET-degrading bacterium, Ideonella sakaiensis, was identified and suggested for possible use in degradation and/or recycling of PET. However, the molecular mechanism of PET degradation is not known. Here we report the crystal structure of I. sakaiensis PETase (IsPETase) at 1.5 Å resolution. IsPETase has a Ser–His-Asp catalytic triad at its active site and contains an optimal substrate binding site to accommodate four monohydroxyethyl terephthalate (MHET) moieties of PET. Based on structural and site-directed mutagenesis experiments, the detailed process of PET degradation into MHET, terephthalic acid, and ethylene glycol is suggested. Moreover, other PETase candidates potentially having high PET-degrading activities are suggested based on phylogenetic tree analysis of 69 PETase-like proteins.
Highlights
Plastics, including poly(ethylene terephthalate) (PET), possess many desirable characteristics and are widely used in daily life
To elucidate the molecular mechanisms of IsPETase, its crystal structure was determined at 1.5 Å resolution (Fig. 1 and Supplementary Fig. 1)
We determined the crystal structure and reported the structural features conferring high PET-degrading activity on IsPETase based on the docking calculations
Summary
Plastics, including poly(ethylene terephthalate) (PET), possess many desirable characteristics and are widely used in daily life. To remove plastic wastes and recycle plastic-based materials, several chemical degradation methods such as glycolysis, methanolysis, hydrolysis, aminolysis and ammonolysis have been developed[3]. These methods generally require high temperature and often generate additional environmental pollutants[4]. A dual enzyme system consisting of Tfcut[2] from T. fusca KW3 and LC cutinase[15] or lipase from C. antarctica and cutinase from Humicola insolens[16] was found to have synergistic effects Despite these attempts, the PET degradation activity still remains low
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