The enantiomeric purity of alcohols formed by enzymatic reduction of ketones can be improved by optimisation of the temperature and by using a high co-substrate concentration.
The stereoselective reduction of ketones by alcohol dehydrogenase from Thermoanaerobium brockii was studied in organic reaction media. 2-Propanol was used as co-substrate to regenerate the coenzyme NADPH. The enantiomeric excess of the alcohol formed from the ketone decreased during the course of the reaction (from 53 to 0% e.e. in the formation of (R)-2-butanol). This was interpreted as being due to the reversibility of all the reactions involved. By using a large excess of 2-propanol this effect was suppressed. In the reduction of 2-butanone to (R)-2-butanol, the enantiomeric excess increased with increasing temperature, but in the reduction of 2-pentanone to (S)-2-pentanol the enantiomeric excess decreased with increasing temperature. The data were evaluated in terms of free energy of activation of the reaction pathways leading to the different possible products.
Yang
H
H
Department of Biotechnology, Center for Chemistry and Chemical Engineering, Lund University, Sweden.
Jönsson
A
A
Wehtje
E
E
Adlercreutz
P
P
Mattiasson
B
B
D000433:1-Propanol / Q000737:chemistry; D000426:Alcohol Dehydrogenase / Q000737:chemistry; D001419:Bacteria / Q000201:enzymology; D000440:Butanols / Q000737:chemistry*; D002074:Butanones / Q000737:chemistry*; D003080:Cold Temperature; D007700:Kinetics; D009994:Osmolar Concentration; D013237:Stereoisomerism; D013379:Substrate Specificity; D013816:Thermodynamics
D000440:Butanols; D002074:Butanones; C043958:2-butanol; C005222:methylethyl ketone; D000433:1-Propanol; D000426:Alcohol Dehydrogenase