Formation and Reduction of Intermediate Acyladenylate by Aryl‐Aldehyde

The enzyme aryl‐aldehyde: NADP oxidoreductase catalyzes a rapid exchange of PPi and ATP. The reaction requires the presence of an aromatic acid and Mg 2+ ions. The exchange reaction has a pH‐optimum of approx. 8.5 and is inhibited by NADPH. The inhibition of the exchange reaction by hydroxylamine as well as the enzymic formation of benzoylhydroxamate confirm that an activated intermediate is involved in the reduction of aromatic acids. This compound was identified as acyladenylate which, however, is assumed not to exist in the free state under normal conditions. In a subsequent step the acyladenylate is reduced to aldehyde. This reaction depends on the presence of sulfhydryls and does not require Mg 2+ ions. Both the activating and the reductive step are catalyzed by one enzyme.