Year: 2026
Type: preprint
Abstract: Polyurethane (PU) low-cost production and versatility propelled its widespread daily usage. However, due to a lack of efficient end-of-life waste treatment options, this recalcitrant polymer tends to accumulate, becoming hazardous. Enzyme depolymerization emerged as a promising 2 alternative to tackle this global problem. Accordingly, three metagenome-based urethanases were discovered (UMG-SP1, 2 and 3). Despite several efforts being made to understand their catalysis, none of the studies accounted for full protein sampling. To address this, we employed an umbrella sampling-based quantum mechanics/molecular mechanics methodology to explore UMG-SP3catalyzed urethane bond hydrolysis. Our results revealed that the hydrolytic mechanism occurred in two sequential stages: i) acylation; and ii) deacylation. The first stage was rate-limiting, with an energetic barrier of 21.6 kcal.mol-1, corresponding to the formation of the acyl-enzyme state and the release of an alcohol (leaving group). Remarkably, the energetic barrier was in agreement with the previously reported values for the UMG-SP2 homolog. In addition, the enzyme shown preference for the cleavage of the C-O bond instead of the C-N bond. However, we observed that the overall reaction was endergonic, with a product-state Gibbs free energy of 8.3 kcal.mol-1. UMG-SP3 has previously been shown to be less stable than the other UMG-SPs. As a result, its more mobile active site may be less effective at stabilizing the released product, increasing the associated free energy. Hence, to improve the likelihood of industrial implementation, the mechanistic data should be leveraged to rationally engineer a more stable and efficient enzyme. Altogether, these findings can pave the way for improving enzymatic depolymerization of PU.
Source: ChemRxiv
Language: English
Subfield: Organic Chemistry
Field: Chemistry
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W7220665069