ABSTRACT
The data available provide a rather detailed picture of the evolution and structure of human aldehyde oxidase (AOX), although the physiological functions of this class of enzymes is obscure. Vertebrate AOXs and xanthine oxidoreductase are characterized not only by high levels of similarity in terms of their amino acid sequence, but also as far as the structure of the corresponding genes is concerned. The development of efficient systems for the production and isolation of catalytically active mammalian AOX proteins is of fundamental importance to the study of the substrate specificity of this class of enzymes. Mammalian AOXs are characterized by broad substrate specificity and recognize a variety of organic molecules regardless of the presence of an aldehyde function. AOXs metabolize not only drugs, but also various molecules of toxicological interest, such as phthalazines, which are environmental pollutants and are typical AOX substrates. In the drug-development field, AOX-dependent metabolism is becoming a serious problem.
