Characterization and engineering of a plastic-degrading aromatic polyesterase

Abstract

SignificanceSynthetic polymers are ubiquitous in the modern world but pose a global environmental problem. While plastics such as poly(ethylene terephthalate) (PET) are highly versatile, their resistance to natural degradation presents a serious, growing risk to fauna and flora, particularly in marine environments. Here, we have characterized the 3D structure of a newly discovered enzyme that can digest highly crystalline PET, the primary material used in the manufacture of single-use plastic beverage bottles, in some clothing, and in carpets. We engineer this enzyme for improved PET degradation capacity and further demonstrate that it can also degrade an important PET replacement, polyethylene-2,5-furandicarboxylate, providing new opportunities for biobased plastics recycling.

Structural studies reveal the molecular mechanism of PETase

“…To get insights into the molecular mechanism of PETase, solving high-resolution crystal structure of the enzyme is of vital importance. Additional remote substrate-binding subsites have been proposed by molecular docking [10,12]. In a recent study, a number of PET hydrolase candidates were identified via searching homologous sequences from environmental metagenomes [23].…”

“…Significantly, I. sakaiensis secretes a unique cutinase-like enzyme, later dubbed PETase, to hydrolyze PET to bis(2-hydroxylethyl) TPA (BHET), mono(2-hydroxyethyl) TPA (MHET), and TPA ( Fig. Here, we summarize the most recent studies of crystal structures of PETase and its complex with substrate/product analogs reported by ourselves and other groups [9][10][11][12][13]. Under physiological conditions (30°C, pH 7.0), the enzyme is 5.5-to 120-fold more efficient than previously reported PET-hydrolyzing homologs.…”

“…Recently, we and other groups independently reported the crystal structure of PETase [9][10][11][12][13]. The enzyme adopts a typical a/b-hydrolase fold, containing a twisted central b-sheet consisting of nine b-strands which is sandwiched by six a-helices ( Fig.…”

“…2A). On the other hand, Austin et al [10] introduced two mutations in an adjacent region to make the putative secondary substrate-binding cleft narrower; the resulting enzyme exhibits higher efficiency in reducing PET crystallinity. Interestingly, the active site of PETase seems to be wider than the other cutinases ( Fig.…”

A planet too rich in fibre

“…In April 2018, a paper in the Proceedings of the National Academy of Sciences described an engineered enzyme that can break down polyethylene terephthalate-commonly known as PET-in the water [11]; after an earlier discovery of a PET-degrading bacterium by Japanese scientists [12]. In April 2018, a paper in the Proceedings of the National Academy of Sciences described an engineered enzyme that can break down polyethylene terephthalate-commonly known as PET-in the water [11]; after an earlier discovery of a PET-degrading bacterium by Japanese scientists [12].…”