A research team has discovered a molecular mechanism that demonstrates the degradability of polyethylene terephthalate.

The researchers from the Korea Advanced Institute of Science and Technology simultaneously determined the 3D crystal structure of Ideonella sakaiensis (Is) PETase and developed a new variant with enhanced PET degradation properties.

The research predicts a special molecular mechanism based on the docking simulation between PETase and a PET alternative mimic substrate. The researchers succeeded in constructing a variant for IsPETase with enhanced PET-degrading activity using structural-based protein engineering.

This PET-degrading bacterium called Ideonella sakaiensis was recently identified for its potential to degrade and recycle PET by a Japanese team in the journal Science (Yoshida et al., 2016). However, the detailed molecular mechanism of PET degradation was not identified in that research.

The engineering research team at KAIST, led by Professor San Yup Lee of the Department of Chemical and Biomolecular Engineering and by Professor Kyung-Jin Kim of the Department of Biotechnology at the Kyungpook National University, conducted additional research and reported their findings in the journal Nature Communications on Jan. 26.

The research teams investigated how the substrate binds to the enzyme and which differences in enzyme structure result in significantly higher PET degrading activity compared with other cutinases and esterases, which make IsPETase highly attractive for industrial applications toward PET waste recycling.

“PET is [a] very important source in our daily lives,” the researchers say in a paper. “However, PET after use causes tremendous contamination issues to our environment due to its non-biodegradability … Conventionally, PET is disposed of in landfills, using incineration and sometimes recycling using chemical methods, which induces additional environmental pollution. Therefore, a new development for highly effective PET degrading enzymes is essential to degrade PET using bio- based eco-friendly methods.”

The discovery could lead to new approaches and other enzymes capable of degrading not only PET but other plastics, too.

“Environmental pollution from plastics remains one of the greatest challenges worldwide with the increasing consumption of plastics,” says Lee. “We successfully constructed a new superior PET-degrading variant with the determination of a crystal structure of PETase and its degrading molecular mechanism. This novel technology will help further studies to engineer more superior enzymes with high efficiency in degrading. This will be the subject of our team’s ongoing research projects to address the global environmental pollution problem for the next generation.”