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The unique salt bridge network in GlacPETase: a key to its stability
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Researchers identified a unique salt bridge network in GlacPETase, a cold-adapted PET-degrading enzyme isolated from a glacial metagenome, that enables it to break down plastic at low temperatures. Unlike mesophilic PETases, this enzyme maintains structural flexibility and catalytic activity in cold environments through these stabilizing electrostatic interactions. The findings offer insights for engineering more efficient plastic-degrading enzymes suited to cold-climate bioremediation applications.
The extensive accumulation of polyethylene terephthalate (PET) has become a critical environmental issue. PET hydrolases can break down PET into its building blocks. Recently, we identified a glacial PET hydrolase GlacPETase sharing less than 31% amino acid identity with any known PET hydrolases. In this study, the crystal structure of GlacPETase was determined at 1.8 Å resolution, revealing unique structural features including a distinctive N-terminal disulfide bond and a specific salt bridge network. Site-directed mutagenesis demonstrated that the disruption of the N-terminal disulfide bond did not reduce GlacPETase's thermostability or its catalytic activity on PET. However, mutations in the salt bridges resulted in changes in melting temperature ranging from -8°C to +2°C and the activity on PET ranging from 17.5% to 145.5% compared to the wild type. Molecular dynamics simulations revealed that these salt bridges stabilized the GlacPETase's structure by maintaining their surrounding structure. Phylogenetic analysis indicated that GlacPETase represented a distinct branch within PET hydrolases-like proteins, with the salt bridges and disulfide bonds in this branch being relatively conserved. This research contributed to the improvement of our comprehension of the structural mechanisms that dictate the thermostability of PET hydrolases, highlighting the diverse characteristics and adaptability observed within PET hydrolases.IMPORTANCEThe pervasive problem of polyethylene terephthalate (PET) pollution in various terrestrial and marine environments is widely acknowledged and continues to escalate. PET hydrolases, such as GlacPETase in this study, offered a solution for breaking down PET. Its unique origin and less than 31% identity with any known PET hydrolases have driven us to resolve its structure. Here, we report the correlation between its unique structure and biochemical properties, focusing on an N-terminal disulfide bond and specific salt bridges. Through site-directed mutagenesis experiments and molecular dynamics simulations, the roles of the N-terminal disulfide bond and salt bridges were elucidated in GlacPETase. This research enhanced our understanding of the role of salt bridges in the thermostability of PET hydrolases, providing a valuable reference for the future engineering of PET hydrolases.
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Researchers used molecular dynamics simulations and lab assays to compare two PET-degrading enzymes at different salt concentrations, finding that the marine-derived PETaseSM14 maintains activity under high-salt conditions due to a rigid binding pocket, while the commonly studied IsPETase is deactivated by high ionic strength, offering insights for engineering enzymes suited to diverse environments.
A third type of PETase from the marine Halopseudomonas lineage
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Researchers identified a previously unknown class of PET-degrading enzyme (PETase) from marine Halopseudomonas bacteria, expanding the known diversity of plastic-degrading enzymes in ocean environments. This discovery adds to the growing catalog of marine microorganisms capable of breaking down polyethylene terephthalate, a widely used plastic.
In silico structural analysis and biochemical characterization of a novel PETase from Antarctic Streptomyces sp .
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Researchers characterized a novel PET-degrading enzyme (SsPETase) from Antarctic Streptomyces bacteria, using AlphaFold structural prediction and molecular dynamics simulations to reveal key catalytic residues and a substrate-dependent conformational shift that activates the enzyme, providing a foundation for engineering more efficient plastic-degrading enzymes.
Computational Engineering of a Thermostable Enzyme for the Degradation of PET Through Manipulation of Disulfide Bonds
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Researchers used computational protein engineering to introduce additional disulfide bonds into the FAST-PETase enzyme structure, finding that increased disulfide bond density enhanced thermal stability beyond existing benchmarks, pointing toward a rational design path for more industrially viable PET-degrading biocatalysts.
Computational Engineering of a Thermostable Enzyme for the Degradation of PET Through Manipulation of Disulfide Bonds
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Researchers used computational protein engineering to introduce additional disulfide bonds into the FAST-PETase enzyme structure, finding that increased disulfide bond density enhanced thermal stability beyond existing benchmarks, pointing toward a rational design path for more industrially viable PET-degrading biocatalysts.
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