Plastic pollution in the marine environment has skyrocketed in the past decades making it a serious environmental challenge to address. The application of plastic-degrading enzymes, as a bio-based solution, paved the way for rigorous enzyme discovery. Here, we identified two novel marine hydrolases. The MAG7-target and MAG1-target, from metagenome-assembled genomes (MAGs) from enrichment cultures collected from deep-sea Ægir hydrothermal vents. The MAG7-target and MAG1-target are affiliated with reconstructed genomes which share taxonomic similarity with Pelagibacterium sp. and Paraburkholderia sp., respectively. Functional screening showed potential promiscuous activity in the depolymerization of PCL and PU, while, inactivity on BHET plates. The novel hydrolases showed structures of alpha/beta-foldings with high similarity to known hydrolases such as leaf-branch compost (LCC), Pseudomonas mendocina lipase, Ideonella sakaiensis (IsPETase), and Vibrio gazogenes (PET6) based on the sequence feature and structural superimposition. A new approach using structure-based homology for enzyme discovery was performed. Cluster network analysis determined the human butyrylcholinesterase (rBChE) co-localized with the MAG1-target. Active degradation of rBChE and hBChE on the BHET plate was confirmed. The elucidation of rBChE crystal structure shared conserved similarity to known BHETases, BsEst and p-nitrobenzyl from Bacillus subtilis. These results suggest the potential new function of this human enzyme as BHETases.
Keywords
Extreme environments, promiscuous enzymes, plastic degradation, functional screening, BHETases
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