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Computer-directed rational engineering of dioxygenase TcsAB for triclosan biodegradation under cold conditions

Summary

Scientists engineered a special enzyme called TcsAB to work better at cold temperatures, enabling it to break down triclosan, a harmful antibacterial chemical that pollutes our water. By using computer simulations and strategic mutations, they created a modified enzyme that degrades triclosan 2.5 times more efficiently at 15°C. When inserted into bacteria, this engineered enzyme helps clean up triclosan pollution in natural environments without requiring energy-intensive heating.

Background

Triclosan (TCS) is a broad-spectrum antibacterial agent that accumulates in aquatic environments and poses risks to aquatic organisms and human health due to bioaccumulation, endocrine-disrupting, and reproductive toxicity effects. The dioxygenase TcsAB is the only known specific enzyme capable of degrading TCS, but exhibits significantly reduced activity under cold conditions, limiting practical bioremediation applications.

Objective

To engineer the dioxygenase TcsAB using computer-directed rational design combining loop engineering and N-terminal truncation to enhance its catalytic activity at low temperatures, enabling efficient TCS biodegradation at ambient environmental conditions.

Results

The iterative mutant TcsAB (TcsA Y277P/F279P/S311W/A313W with TcsB N-terminal truncation) exhibited 2.54-fold greater catalytic efficiency than wild-type at 15°C, with kcat values 2.94-fold higher. Molecular dynamics simulations revealed increased substrate-binding pocket flexibility and greater hydrogen bonding formation with TCS in the mutant, facilitating enhanced catalytic activity.

Conclusion

Rational engineering of dioxygenase TcsAB successfully enhanced its cold-temperature catalytic activity, creating an engineered strain capable of efficient TCS degradation at low temperatures. This approach provides theoretical guidance for enzyme redesign to improve bioremediation of emerging contaminants under realistic environmental conditions while reducing energy costs.
  • Published in:Applied and Environmental Microbiology,
  • Study Type:Experimental Research,
  • Source: 10.1128/aem.00346-25; PMID: 40042274
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