InterPro domain: IPR036856

Aldehyde oxidase ( 1.2.3.1 ) catalyses the conversion of an aldehyde in the presence of oxygen and water to an acid and hydrogen peroxide. The enzyme is a homodimer, and requires FAD, molybdenum and two 2FE-2S clusters as cofactors. Xanthine dehydrogenase ( 1.1.1.204 ) catalyses the hydrogenation of xanthine to urate, and also requires FAD, molybdenum and two 2FE-2S clusters as cofactors. This activity is often found in a bifunctional enzyme with xanthine oxidase ( 1.1.3.22 ) activity too. The enzyme can be converted from the dehydrogenase form to the oxidase form irreversibly by proteolysis or reversibly through oxidation of sulphydryl groups.

The aldehyde oxidase and xanthine dehydrogenase, a/b hammerhead domain is an evolutionary conserved protein domain [ 1 , 2 ]. The core structure of this domain has a beta-BETA-alpha-beta-BETA-beta-alpha fold and contains a beta-hammerhead motif similar to that in barrel-sandwich hybrids.

1. Crystal structure of the xanthine oxidase-related aldehyde oxido-reductase from D. gigas. Science 270, 1170-6
2. Crystal structure and mechanism of CO dehydrogenase, a molybdo iron-sulfur flavoprotein containing S-selanylcysteine. Proc. Natl. Acad. Sci. U.S.A. 96, 8884-9