User:Emily Hwang/Sandbox1
From Proteopedia
Contents |
Biochemical Results
Improved Thermal Stability
Thermal stability is very important for enzyme-catalyzed PET degradation because the reaction must take place above the transition temperature of PET(70ºC), which allows the substrate to have optimal flexibility to fit into the active site. The disulfide bridge mutation raises the melting point of the enzyme from 84.7ºC to 94.5ºC.[1] The covalent disulfide bond allows the tertiary structure of the enzyme to maintain its integrity at higher temperatures.
Depolymerization Efficiency of Mutant LCCs
Both the ICCG and WCCG mutants designed by Tournier et al. exhibited a greater depolymerization efficiency than the wild type. The wild type LCC reached 53% depolymerization in 20 hours while both the ICCG and WCCG mutants reached 90% depolymerization in 10.5 hrs and 9.3 hrs respectively.[1]
Enhanced Catalytic Efficiency
The ICCG and WCCG mutations constructed by Tournier et al. restored catalytic activity to that of the wild type and beyond the wild type. The WCCG quadruple mutation showed a 122% increase in catalysis, with an increased ability to sustain its structure at temperatures 6.2 degrees higher than the wild type (84.7 degrees Celsius).[1] The ICCG quadruple mutation showed a 2% decrease in activity compared to the wild type, but a thermal stability increase by 10.1 degrees Celsius.[1] The increase in specific activity of the F243W mutation could be attributed to the hydrogen bond formed between the amine group on tryptophan and a carbonyl oxygen of the -1 monomer, with the aromatic ring in W243 retaining pi-stacking and Van der Waals interactions made by F243 in the wild type. These additional intermolecular forces between the active site and the ligand likely led to improved binding affinity which increased specific activity.
Conclusions
Implications for Plastic Recycling
Enzyme-catalyzed plastic degradation produces less NaSO4 than other recycling processes. Current standard recycling processes produce approximately 80% NaSO4 by weight of recycled material, while this recycling process produces only 60% NaSO4 by weight of recycled material. There are many negative environmental impacts of NaSO4 including acid rain, respiratory health concerns, reduced visibility due to light refraction by atmospheric particles, and disrupting aquatic ecosystems. Therefore, it is essential to mitigate NaSO4 waste produced in recycling processes. This improved enzyme-catalyzed mechanism of PET depolymerization has important implications in horizontal recycling (LINK), and could help to close the loop of the circular economy. The LCC mutant engineered by Tournier et al. is a promising aid in the issue of excessive plastic disposal.
