Symmetry breaking by enzyme-catalyzed epoxide hydrolysis

Area of Science:

• Biocatalysis and Enzyme Mechanisms
• Stereoselective Organic Synthesis
• Structural Biology

Background:

• Epoxide hydrolases are crucial enzymes in epoxide metabolism and detoxification.
• Understanding enzyme selectivity is key for developing biocatalytic applications.
• Methylstyrene oxide stereoisomers present a challenge for selective enzymatic hydrolysis.

Purpose of the Study:

• To elucidate the factors governing the stereoselective ring opening of methylstyrene oxide by epoxide hydrolase StEH1.
• To identify the stereo-differentiating step in the enzymatic hydrolysis mechanism.
• To provide insights into the substrate-enzyme interactions of StEH1.

Main Methods:

• Enzymatic assays using methylstyrene oxide stereoisomers and epoxide hydrolase StEH1.
• Kinetic analysis to determine reaction rates and selectivity.
• Mechanistic studies involving the characterization of reaction intermediates.

Main Results:

• Epoxide hydrolase StEH1 exhibits significant stereoselectivity in the hydrolysis of methylstyrene oxide.
• The stereo-differentiating step was identified as the selective hydrolysis of an alkylated intermediate.
• This intermediate is formed via the reaction of the epoxide with an aspartyl residue in the enzyme's active site.

Conclusions:

• The stereoselectivity of StEH1 is determined by the precise hydrolysis of a transient alkylated intermediate.
• The enzyme's active site architecture dictates the selective recognition and reaction of specific stereoisomers.
• These findings contribute to the understanding of epoxide hydrolase mechanisms and stereoselective biocatalysis.