In-silico and biochemical insights into MHET biodegradation by Arctic Pseudomonas MHET hydrolase

Plastic pollution poses a significant threat to the Arctic ecosystem, primarily due to long-distance transport and localized anthropogenic activities. This study examines the plastic-degrading bacteria from the Arctic, with a focus on Pseudomonas sp. PAMC26590, which degrades mono(2-hydroxyethyl) terephthalate (MHET). Genomic analysis of this strain revealed a putative MHET hydrolase gene involved in MHET degradation, as supported by in-silico methods. The strain has a 6.2 Mb circular chromosome with 60 % GC content, 5287 coding genes, 64 tRNAs, and 16 rRNAs. Under the optimized conditions (20 °C, pH 7.0, mineral salt medium), Pseudomonas degraded 58.33 % of MHET (83 ng/mL) within 7 days, demonstrating cold-adapted degradation capability. Thus, we present our discovery of the Arctic strain Pseudomonas sp. PAMC26590 has shown the ability to degrade MHET at low temperatures for the first time. Furthermore, recombinant MHET hydrolase showed 79 % biodegradation activity at pH 8.0 and 25 °C. Molecular docking revealed a strong binding affinity (ΔG = -6.67 kcal/mol) mediated by the catalytic residues Ser199, His457, and Asp416, supported by stabilizing van der Waals interactions, which suggests a biologically plausible binding mode. Molecular dynamics (MD) simulations and MM-GBSA calculations confirmed structural stability and energetically favorable binding (ΔGbind = -65.42 kcal/mol), reinforcing the ligand's potential role in the catalytic mechanism of MHET hydrolase.