Scope and limitations of the use of nicotinoprotein alcohol dehydrogenase for the coenzyme-free production of enantiopure fine-chemicals

Nicotinoprotein alcohol dehydrogenases are enzymes that contain non-dissoci able NAD(P)(H) in the active site. The suitability of a nicotinoprotein alc ohol dehydrogenase as coenzyme-independent alternative to classic alcohol d ehydrogenases for enantioselective synthetic applications was studied. To t his end the NADH-containing nicotinoprotein, np-ADH, from Rhodococcus eryth ropolis DSM 1069 was used as a model enzyme in different types of conversio n: asymmetric synthesis, kinetic resolution and racemization. The enzyme wa s found to catalyze the asymmetric reduction of ketones using cheap reducta nts, such as ethanol, with high stereoselectivity, but the reaction was too slow to obtain good yields. Kinetic resolutions of racemic alcohols failed due to dismutation of the aldehyde that was used as cosubstrate. Racemizat ion of a secondary alcohol via the corresponding ketone could not be achiev ed, which was due to an unidentified side reaction. This evaluation shows t hat, for developing bio transformations of industrial interest using nicoti noprotein alcohol dehydrogenases, the attention should be focused on enzyme s with a higher reactivity towards prochiral ketones and secondary alcohols .