How Medium Affects the Activity and Stereopreference of Thermoanaerobacter ethanolicus Secondary Alcohol Dehydrogenase Catalyzed Reduction of Ketones

Title:How Medium Affects the Activity and Stereopreference of Thermoanaerobacter ethanolicus Secondary Alcohol Dehydrogenase Catalyzed Reduction of Ketones

Volume: 20 Issue: 5

Author(s): Ibrahim Karume*, Simon Bbumba and Simon Tewolde

Affiliation:

• Department of Chemistry, Makerere University, Kampala, P. O. Box 7062, Uganda

Abstract: The activity and selectivity of W110G Thermoanaerobacter ethanolicus secondary alcohol dehydrogenase were altered by cosubstrate and cosolvent at varying temperatures. A sharp drop in the enantiomeric excess (ee) was observed at 60°C in the first 3 h, suggesting increased selectivity mistakes in the reduction of 4-phenyl-2-butanone to the expected (S)-4-phenyl-2-butanol using 5% v/v of 2-propanol as a cosubstrate. The ee increased exponentially with cosubstrate concentration, reaching ≥94% with 30-70% v/v 2-propanol. However, a decrease in enzyme activity was noticed at ≥30% v/v 2-propanol by a sharp drop in conversion. The lowest ee (<3%) was registered using 5% v/v 2- propanol at 30-40°C, which prolonged enzyme life that allowed reversible redox reaction with selectivity mistakes to give the R-alcohol compared to ≥18% ee at 50-60°C, where faster reaction rates promoted selectivity mistake, but enzyme life was shortened by protein denaturation at the elevated temperatures. Water-miscible and immiscible organic cosolvents (25% v/v) increased enzyme selectivity. For methanol, ethanol, ethylene glycol and tert-butanol, the activity/conversion decreased with an increase in pKa and log P while the stereoselectivity/ee increased.

Cite this article as:

Karume Ibrahim*, Bbumba Simon and Tewolde Simon, How Medium Affects the Activity and Stereopreference of Thermoanaerobacter ethanolicus Secondary Alcohol Dehydrogenase Catalyzed Reduction of Ketones, Letters in Organic Chemistry 2023; 20 (5) . https://dx.doi.org/10.2174/1570178620666221021103540