Enantioselective Conversions of the Racemic C₃-Alcohol Synthons, Glycidol (2, 3-Epoxy-1-propanol), and Solketal (2, 2-Dimethyl-4-(hydroxymethyl)-1, 3-dioxolane) by Quinohaemoprotein Alcohol Dehydrogenases and Bacteria Containing Such Enzymes

Abstract

Several purified or commercially available alcohol oxidoreductases of different kinds were tested for their ability to convert the racemic, glycerol-based C₃-synthons glycidol (2, 3-epoxy-1-propanol) and solketal (2, 2-dimethyl-4-(hydroxymethyl)-1, 3-dioxolane), with adequate activity and enantioselectivity. Quinohaemoprotein alcohol dehydrogenases (enzymes containing haem c as well as pyrroloquinoline quinone (PQQ) as cofactors) appeared to be excellently suited for such use. The bacteria from which the enzymes were purified had the same enantiomer preference and had an efficient respiratory chain for reoxidation of these dehydrogenases. In some cases, however, whole cells gave a lower enantiomer ratio (E) than the pure enzyme. NAD-dependent alcohol dehydrogenases also are present in these bacteria, but their presence may not explain the lower ratio because they oxidized the C₃-synthons little if at all. It seems, therefore, that different kinetic mechanisms are responsible for the discrepancy between the effects of whole cells and purified enzymes.