New Deep-Sea Enzyme Discovered: PET Plastic Breakdown for the First Time

Researchers from the University of Hamburg and Heinrich-Heine University Düsseldorf played a significant role in the microbiological research. This discovery vastly expands the knowledge of PET-degrading enzymes, their underlying mechanisms, and the evolutionary understanding of their diversity across global oceans. The research team recently published their findings in Communications Chemistry, where they explore both the biotechnological applications and the crucial implications for biogeochemical processes in marine and terrestrial environments.

Research Highlight: The Discovery of PET46

Professor Ruth Schmitz-Streit, head of the Molecular Biology of Microorganisms group at the Institute of General Microbiology (IfAM) and member of Kiel Marine Science (KMS), emphasized the importance of this finding: "In our study, we have discovered a new genetic resource from deep-sea organisms belonging to archaea that degrades PET." Previously, around 80 PET-degrading enzymes had been identified, mostly from bacteria and fungi. "Our findings contribute to a better understanding of the ecological role of deep-sea archaea and their potential role in degrading PET waste in the ocean," Schmitz-Streit added.

PET46's Unique Properties

Using a metagenomic approach, the team identified and biochemically characterized a PET-degrading enzyme, named PET46, from a non-cultured deep-sea microorganism for the first time. They identified the gene from a deep-sea sample based on its similarity to known sequences, synthesized the corresponding coding gene, produced the enzyme in Escherichia coli, and studied it biochemically and structurally. PET46 has unique features that add to the diversity of PET-active enzymes. Structurally distinct from previously discovered enzymes, PET46 is capable of degrading both long-chain PET polymers and short-chain oligomers, allowing for continuous degradation.

The enzyme also employs a different mechanism for substrate binding compared to known PET-degrading enzymes. Researchers identified an unusual "lid" of 45 amino acids above the enzyme's active center, which is crucial for binding. In contrast, other PET enzymes typically feature aromatic amino acids near their active sites.

Promising Biotechnological Applications

On a molecular level, PET46 shares similarities with ferulic acid esterase, an enzyme that breaks down the natural polymer lignin found in plant cell walls. This enzyme releases sugars from woody plant parts by degrading lignin polymers. Due to the structural similarities between lignin and PET, naturally occurring PET-degrading enzymes may also play a key role in composting wood in forest soils.

The biochemical properties of PET46 make it a promising candidate for degrading plastics both in marine and terrestrial environments, as well as for potential biotechnological applications. Compared to other well-characterized PET-degrading enzymes from bacteria and compost plants, PET46 operates more efficiently at 70°C than these reference enzymes at their respective optimal temperatures.