Inhibition of horse liver and yeast alcohol dehydrogenase by aromatic and aliphatic aldehydes

The reactivity of yeast alcohol dehydrogenase (YADH) and horse liver alcohol dehydrogenase (HLADH) towards 12 different aldehydes was tested. YADH was inhibited by pre-incubation with citral, citronellal, p-cuminaldehyde, p-anisaldehyde, m-tolualdehyde, trans-cinnamaldehyde, salicylaldehyde, p-hydroxybenzaldehyde and benzaldehyde, although of these aldehydes only trans-cinnamaldehyde acted as a substrate for the enzyme. HLADH was inhibited, to a much smaller extent, by pre-incubation with citral, salicylaldehyde, citronellal, p-anisaldehyde, piperonaldehyde, trans-cinnamaldehyde, p-hydroxybenzaldehyde and p-cuminaldehyde and all of these aldehydes acted as substrates for the HLADH. Immobilisation of the enzymes on CNBr-activated Sepharose 4B gave protection against inhibition by the aldehydes, suggesting a means of significantly extending the useful lifetime of the enzymes when they are used in industrial processes.