ALDH genes were retrieved from Entrez Gene [12] using the terms 'ALDH' or 'aldehyde dehydrogenase'. Peptide sequences for each ALDH gene were retrieved from Entrez Protein [12] and aligned against a reference list of ALDH family members, including known human ALDHs and sequences from the NCBI's HomoloGene [12] using ClustalW [13]. To be included for description, a gene record was required to meet three criteria: 1) the protein product of the gene must be 'full-length' (ie excludes known fragments and partial records); 2) the gene must have a known unique chromosomal location on the annotated genome; and 3) the gene must be listed as protein-coding (ie excludes known pseudogenes).
