A team of researchers from the University of Greifswald and Helmholtz-Zentrum-Berlin (HZB) has found a solution for the molecular structure of the vital enzyme MHETase at BESSY II. MHETase was discovered in bacteria and when paired with another enzyme, PETase it can break down plastic PET into its basic building blocks. The 3D structure has allowed researchers to create a MHETase variant to utilize it in combination with PETase for sustainable recycling of PET.
Dr. Gert Weber, biochemist and structural biologist, explains that MHETase has a larger and more complex structure than PETase and an individual MHETase molecule comprises of 600 amino acids or 4000 atoms. The molecule’s surface is twice the size of that of PETase, which is why it has more potential to optimize the space in the decomposition of PET. Weber along with Prof. Uwe Bornscheuer, biotechnologist, at the Institute of Biochemistry, worked to develop the idea of solving the structure of MHETase and then utilizing the knowledge obtained in enhancing the enzyme for applications in the recycling of PET. The process involved the extraction of the enzyme from bacterial cells followed by its purification to achieve the complex 3D structure of MHETase. The researchers cut up a PET bottle, decomposed the PET polymer using chemicals and synthesized a tiny fragment from it that binds to the MHETase without being cleaved by it. The team then grew small crystals from the ‘blocked’ MHETase that allowed them to watch how the molecule works and use these insights in strategizing the applications of the enzyme.
Both enzymes still need to be perfected and the scientists aim to work on the systematic development of both enzymes before they can efficiently decompose PET. Weber will carry out further studies on the biological structures to facilitate their environmental applications. These enzymes can break down PET plastics and other polymers into building blocks, which can be vital for recycling and will be a long-term solution for the plastic waste problem.