Aldehydes are produced as intermediates during the metabolism of many different compounds including amino acids, carbohydrates, lipids vitamins and steroids [PMID:11154732]. They are highly reactive compounds whose buildup to excess levels can cause cytotoxic, genotoxic and carcinogenic effects. Aldehyde dehydrogenases oxidise these compounds to their respective carboxylic acids. This is necessary both for the operation of these metabolic pathways, and to prevent the concentration of aldehydes within the cell from reaching toxic levels. Proteins in this entry are NAD(P)-dependent aldehyde dehydrogenases, found in a variety of organisms, including general aldehyde dehydrogensases (EC: 1.2.1.5), fatty aldehyde dehydrogenases (EC: 1.2.1.3), and coniferyl aldehyde dehydrogenase (EC: 1.2.1.68). Structural studies of the Rattus norvegicus protein (SWISSPROT: P11883) show that this enzyme is a homodimer where each subunit consists of two alpha-beta-alpha domains [PMID:9095201]. The mode of NAD binding differs substantially from that commonly associated with the Rossman fold.