Many of these proteins have been defined based on genomic or dbEST data and have not been studied extensively. Many records remain in databases that are listed as 'protein-coding' but which instead may represent pseudogenes of various types. Furthermore, although the genes here do not have internal stop codons, without functional analysis, it is difficult to determine whether the genes might have other inactivating mutations or if they experience selective pressure. Although automated prediction and naming of ALDH proteins from completely sequenced genomes have achieved a great deal of information in a short amount of time, the alignment, curation and naming of these genes remains an important task. The fact that no new human ALDH genes have been identified over the past six years and that most other vertebrates seem to have settled close to this number suggests that identification of ALDH superfamily members in vertebrates is nearing completion. Determining the function and biological importance of each family member still requires additional work, however. As more information becomes available, the web database resource at (http://www.aldh.org) (the aldehyde dehydrogenase gene superfamily resource center)[35] will be updated to reflect our current understanding of this diverse and essential gene superfamily.
