<p>Members of this protein family show full length homology to the molybdenum-containing aldehyde oxido-reductase of <taxon tax_id="879">Desulfovibrio gigas</taxon>. Members, however, are found only within species that have, and near those genes that encode, a set of predicted accessory proteins for selenium-dependent molybdenum hydroxylases. The best known examples of such enzymes are forms of xanthine dehydrogenase and purine hydroxylase; this family appears to be another such enzyme.</p>