| 1. |
- Guo, Boyang, et al.
(författare)
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Conformational Selection in Biocatalytic Plastic Degradation by PETase
- 2022
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Ingår i: ACS Catalysis. - : American Chemical Society (ACS). - 2155-5435. ; 12:6, s. 3397-3409
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Tidskriftsartikel (refereegranskat)abstract
- Due to the steric effects imposed by bulky polymers, the formation of catalytically competent enzyme and substrate conformations is critical in the biodegradation of plastics. In poly(ethylene terephthalate) (PET), the backbone adopts different conformations, gauche and trans, coexisting to different extents in amorphous and crystalline regions. However, which conformation is susceptible to biodegradation and the extent of enzyme and substrate conformational changes required for expedient catalysis remain poorly understood. To overcome this obstacle, we utilized molecular dynamics simulations, docking, and enzyme engineering in concert with high-resolution microscopy imaging and solid-state nuclear magnetic resonance (NMR) to demonstrate the importance of conformational selection in biocatalytic plastic hydrolysis. Our results demonstrate how single-amino acid substitutions in Ideonella sakaiensis PETase can alter its conformational landscape, significantly affecting the relative abundance of productive ground-state structures ready to bind discrete substrate conformers. We experimentally show how an enzyme binds to plastic and provide a model for key residues involved in the recognition of gauche and trans conformations supported by in silico simulations. We demonstrate how enzyme engineering can be used to create a trans-selective variant, resulting in higher activity when combined with an all-trans PET-derived oligomeric substrate, stemming from both increased accessibility and conformational preference. Our work cements the importance of matching enzyme and substrate conformations in plastic hydrolysis, and we show that also the noncanonical trans conformation in PET is conducive for degradation. Understanding the contribution of enzyme and substrate conformations to biocatalytic plastic degradation could facilitate the generation of designer enzymes with increased performance.
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| 2. |
- Guo, Boyang, et al.
(författare)
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Fast Depolymerization of PET Bottle Mediated by Microwave Pre-Treatment and An Engineered PETase
- 2023
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Ingår i: ChemSusChem. - : Wiley. - 1864-5631 .- 1864-564X. ; 16:18
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Tidskriftsartikel (refereegranskat)abstract
- Recycling plastics is the key to reaching a sustainable materials economy. Biocatalytic degradation of plastics shows great promise by allowing selective depolymerization of man-made materials into constituent building blocks under mild aqueous conditions. However, insoluble plastics have polymer chains that can reside in different conformations and show compact secondary structures that offer low accessibility for initiating the depolymerization reaction by enzymes. In this work, we overcome these shortcomings by microwave irradiation as a pre-treatment process to deliver powders of polyethylene terephthalate (PET) particles suitable for subsequent biotechnology-assisted plastic degradation by previously generated engineered enzymes. An optimized microwave step resulted in 1400 times higher integral of released terephthalic acid (TPA) from high-performance liquid chromatography (HPLC), compared to original untreated PET bottle. Biocatalytic plastic hydrolysis of substrates originating from PET bottles responded to 78 % yield conversion from 2 h microwave pretreatment and 1 h enzymatic reaction at 30 °C. The increase in activity stems from enhanced substrate accessibility from the microwave step, followed by the administration of designer enzymes capable of accommodating oligomers and shorter chains released in a productive conformation.
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| 3. |
- Stamm, Arne, et al.
(författare)
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Pinene-Based Oxidative Synthetic Toolbox for Scalable Polyester Synthesis
- 2021
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Ingår i: JACS Au. - : American Chemical Society (ACS). - 2691-3704. ; 1:11, s. 1949-1960
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Tidskriftsartikel (refereegranskat)abstract
- Generation of renewable polymers is a long-standing goal toward reaching a more sustainable society, but building blocks in biomass can be incompatible with desired polymerization type, hampering the full implementation potential of biomaterials. Herein, we show how conceptually simple oxidative transformations can be used to unlock the inherent reactivity of terpene synthons in generating polyesters by two different mechanisms starting from the same alpha-pinene substrate. In the first pathway, alpha-pinene was oxidized into the bicyclic verbanone-based lactone and subsequently polymerized into star-shaped polymers via ring-opening polymerization, resulting in a biobased semicrystalline polyester with tunable glass transition and melting temperatures. In a second pathway, polyesters were synthesized via polycondensation, utilizing the diol 1-(1'-chydroxyethyl)-3-(2'-hydroxyethyl)-2,2-dimethylcyclobutane (HHDC) synthesized by oxidative cleavage of the double bond of alpha-pinene, together with unsaturated biobased diesters such as dimethyl maleate (DMM) and dimethyl itaconate (DMI). The resulting families of terpenebased polyesters were thereafter successfully cross-Iinked by either transetherification, utilizing the terminal hydroxyl groups of the synthesized verbanone-based materials, or by UV irradiation, utilizing the unsaturation provided by the DMM or DMI moieties within the HHDC-based copolymers. This work highlights the potential to apply an oxidative toolbox to valorize inert terpene metabolites enabling generation of biosourced polyesters and coatings thereof by complementary mechanisms.
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