This subfamily is named after the only biochemically studied representative, ᴅ-2-hydroxyacid dehydrogenase (ddh) from Haloferax mediterranei, and comprises proteins spread over the taxonomic tree, including eukaryotes (e.g., fungi and protists), archaea and bacteria (cyanobacteria and actinobacteria). Although some archaeal genomes (e.g., a halophilic mesophile Haloferax volcanii) encode as many as four DDH representatives, their function is not known.