An extremely potent anilinoacridine inhibitor of aldehyde oxidase.

An acridine antitumor agent, 4'-(9-acridinylamino)methanesulfon-m-anisidide, has been found to be an extremely potent competitive inhibitor of aldehyde oxidase (EC 1.2.3.1). The inhibitor constant (Ki) was determined to be 0.06 microM. The degree of enzyme inhibition was quite sensitive to small changes in the structure of the inhibitor's anisidide moiety. Drug inhibition was specific for aldehyde oxidase and inhibition was not detected with the other mammalian molybdenum iron-sulfur flavoenzyme, xanthine oxidase (EC 1.2.3.2). Members of the 4'-(9-acridinylamine)methanesulfonanilide series might be useful probes in the study of the structure and function of aldehyde oxidase.