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Light-Activated Electron Transfer and Turnover in Ru-Modified Aldehyde Deformylating Oxygenases
Rajneesh K Bains1, Jessica J Miller1, Hannah K van der Roest1
1Department of Chemistry , Simon Fraser University , 8888 University Drive , Burnaby , British Columbia V5A 1S6 , Canada.
Inorganic Chemistry
|June 26, 2018
Summary
Researchers engineered aldehyde deformylating oxygenase (ADO) enzymes with ruthenium photosensitizers to study electron transfer. These modified enzymes catalyze the conversion of aldehydes to alkanes using light, offering new insights into enzyme mechanisms.
Area of Science:
- Biocatalysis and enzyme engineering
- Bioinorganic chemistry
- Photosensitizer-enzyme conjugates
Background:
- Aldehyde deformylating oxygenase (ADO) enzymes are crucial for converting biological molecules into valuable chemicals.
- Understanding electron transfer mechanisms in ADO is key to optimizing their catalytic efficiency.
- Ruthenium(II) tris-diimine complexes are well-established photosensitizers with tunable redox properties.
Purpose of the Study:
- To engineer ADO enzymes modified with Ru(II) photosensitizers to investigate intramolecular electron transfer.
- To assess the catalytic activity of these novel Ru-ADO constructs in aldehyde conversion.
- To elucidate electron transfer pathways within the modified ADO system.
Main Methods:
- Site-specific modification of wild-type and mutant ADO enzymes with Ru(II) photosensitizers at cysteine residues (C70 and C62).
- Characterization of Ru-ADO constructs using spectroscopic and electrochemical techniques.
- Assay of catalytic activity in the presence of light and a sacrificial reductant for various aldehyde substrates.
Main Results:
- Successful preparation of three Ru-ADO variants, including single-site modification at C70 of wild-type ADO.
- Ru-ADO constructs demonstrated light-driven catalytic turnover of aldehyde substrates.
- Detection of peroxide byproducts for shorter chain aldehydes, indicating substrate-dependent reaction pathways.
Conclusions:
- The Ru-ADO conjugates provide a platform for studying electron transfer dynamics in ADO.
- The photosensitizer acts as an artificial reductase, enabling light-driven catalysis.
- Semiclassical electron transfer theory supports a hopping mechanism for electron flow in both native and modified ADO.
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