Efficient and selective energy transfer photoenzymes powered by visible light

Area of Science:

• Biocatalysis
• Photocatalysis
• Protein Engineering

Background:

• Engineered enzymes with benzophenone sensitizers show potential for stereocontrolled photocatalysis.
• Benzophenone's limitations include ultraviolet light requirement, low efficiency, and restricted chemical scope.

Purpose of the Study:

• To engineer enzymes capable of utilizing visible light for photocatalysis.
• To expand the scope of enzyme-catalyzed photochemical reactions.

Main Methods:

• Engineered an orthogonal Methanococcus jannaschii tyrosyl-tRNA synthetase/tRNA pair for thioxanthone incorporation.
• Developed an enantioselective [2+2] cyclase and an oxygen-tolerant enzyme for C-H insertion.

Main Results:

• Achieved a [2+2] cyclase with significantly enhanced efficiency (kcat = 13 s−1, >1,300 turnovers).
• Developed an enzyme for selective C-H insertion, yielding spirocyclic β-lactams with high selectivity (99% e.e., 22:1 d.r.).
• Demonstrated suppression of substrate decomposition pathways by the photoenzyme.

Conclusions:

• Thioxanthone-containing enzymes efficiently harness visible light for photocatalysis.
• Engineered enzymes offer superior control over excited-state intermediates compared to small-molecule sensitizers.
• This work expands the toolkit for biocatalytic and photocatalytic transformations.