The Reduction of Propionic Anhydride by Aldehyde Dehydrogenase-NADH Mixtures at pH 7

Abstract

Although the oxidation of aldehydes by aldehyde dehydrogenase is usually considered to be irreversible, Hart & Dickinson (1978) have shown that anhydrides of carboxylic acids could be reduced to aldehydes by enzyme.NADH mixtures. In a later study Motion et al (1988) demonstrated that acylation of aldehyde dehydrogenase.NADH complexes by acetic anhydride led to the production of acetaldehyde and NAD⁺ in stoichiometric amounts. It is clear from these results, and the fact that 80% of the initial NADH concentration can be oxidised by anhydrides at an almost constant rate, that there is no intrinsic thermodynamic barrier to the reverse reaction once the appropriate acyl enzyme species is formed. The mechanism for reduction of aldehydes is presumably the reverse of that for aldehyde oxidation (Scheme I).