Biocatalyst-artificial metalloenzyme cascade based on alcohol dehydrogenase

Area of Science:

• Biocatalysis
• Organometallic Chemistry
• Protein Engineering

Background:

• Chemo-enzymatic cascades offer efficient synthesis but face challenges with enzyme-metal catalyst incompatibility.
• Rhodium catalysts with alcohol dehydrogenases can regenerate nicotinamide cofactors but suffer from mutual inactivation.
• Metal binding to enzyme surfaces leads to loss of activity for both components.

Purpose of the Study:

• To develop artificial metalloenzymes by covalently conjugating Rh(iii) catalysts to alcohol dehydrogenase.
• To enhance the stability and efficiency of chemo-enzymatic cascades.
• To create a novel system for NADP+ reduction and cofactor recycling.

Main Methods:

• Covalent conjugation of Rh(iii) catalysts with nitrogen donor ligands to the active site cysteine of Thermoanaerobacter brockii alcohol dehydrogenase (TbADH).
• Utilizing the modified TbADH as a protein scaffold for both alcohol synthesis and cofactor recycling.
• Employing a chemo-enzymatic cascade combining the artificial metalloenzyme with non-modified recombinant enzyme.

Main Results:

• Successful creation of artificial metalloenzymes with Rh(iii) catalysts integrated into the TbADH active site.
• Demonstrated increased stability of both the Rh(iii) catalyst and the alcohol dehydrogenase due to a shielding effect.
• Achieved superior ketone reduction conversions using the novel cascade compared to free metal catalysts.

Conclusions:

• Artificial metalloenzymes can overcome the incompatibility issues between enzymes and transition metal catalysts.
• Covalent conjugation and encapsulation within the enzyme pocket enhance catalyst stability and performance.
• This approach provides a robust platform for efficient chemo-enzymatic transformations.