Confronting PFAS persistence: enzymes catalyzing C-F bond cleavage

Area of Science:

• Biochemistry
• Environmental Science
• Microbiology

Background:

• Enzymatic carbon-fluorine (C-F) bond cleavage research has primarily focused on microbial hydrolases acting on fluoroacetate.
• Biodegrading persistent fluorinated compounds, such as per- and polyfluorinated alkyl substances (PFAS), requires novel enzymes beyond known hydrolases.
• Some hydrolases can target the -CF2- moieties prevalent in PFAS structures.

Purpose of the Study:

• To identify and engineer new enzymes capable of cleaving C-F bonds in recalcitrant fluorinated compounds.
• To explore diverse enzymatic mechanisms, including those catalyzed by reductases, lyases, and oxygenases, for C-F bond degradation.
• To address the challenge of fluoride toxicity, which inhibits bacterial screening and evolution for PFAS defluorination.

Main Methods:

• Screening microbial enzymes for activity against fluorinated compounds.
• Engineering enzymes to enhance C-F bond cleavage efficiency.
• Investigating various enzyme classes (hydrolases, reductases, lyases, oxygenases) for defluorination capabilities.
• Developing strategies to improve bacterial tolerance to fluoride released during C-F bond cleavage.

Main Results:

• Identification of novel enzymatic mechanisms for C-F bond cleavage beyond traditional hydrolases.
• Demonstration that some hydrolases can act on -CF2- groups found in PFAS.
• Recognition that bacterial fluoride tolerance is a significant bottleneck for enzyme evolution and biodegradation applications.

Conclusions:

• Expanding the enzymatic toolkit beyond hydrolases is essential for tackling diverse fluorinated pollutants.
• Enzyme engineering must be coupled with enhanced microbial fluoride tolerance for effective bioremediation of PFAS.
• Further research into reductases, lyases, and oxygenases is needed to broaden enzymatic defluorination strategies.