In higher plants aldehyde oxidases (AO) appear to be homo- and heterodimeric assemblies of AO subunits with probably different physiological functions. AO-delta seems to be involved in the last step of abscisic acid biosynthesis, at least in leaves and seeds. In vitro, AO-delta oxidizes abscisic aldehyde to abscisic acid (ABA). In vitro, AO-delta also uses indole-3-aldehyde (IAld), benzaldehyde, 1-naphthaldehyde and cinnamaldehyde as substrate; the AAO2-AAO3 dimer also uses abscisic aldehyde as substrate.
Also known as Abscisic-aldehyde oxidase (Aldehyde oxidase 3) (AO-3) (AtAO-3) (AtAO4) (Indole-3-acetaldehyde oxidase) (IAA oxidase). Encodes the aldehyde oxidase delta isoform catalyzing the final step in abscisic acid biosynthesis.