Retinoic acid, a hormonally active form of vitamin A, is produced in vivo in a two step process: retinol is oxidized to retinal and retinal is oxidized to retinoic acid. Retinal dehydrogenase type II (RalDH2) catalyzes this last step in the productio ...
Retinoic acid, a hormonally active form of vitamin A, is produced in vivo in a two step process: retinol is oxidized to retinal and retinal is oxidized to retinoic acid. Retinal dehydrogenase type II (RalDH2) catalyzes this last step in the production of retinoic acid in the early embryo, possibly producing this putative morphogen to initiate pattern formation. The enzyme is also found in the adult animal, where it is expressed in the testis, lung, and brain among other tissues. The crystal structure of retinal dehydrogenase type II cocrystallized with nicotinamide adenine dinucleotide (NAD) has been determined at 2.7 A resolution. The structure was solved by molecular replacement using the crystal structure of a mitochondrial aldehyde dehydrogenase (ALDH2) as a model. Unlike what has been described for the structures of two aldehyde dehydrogenases involved in the metabolism of acetaldehyde, the substrate access channel is not a preformed cavity into which acetaldehyde can readily diffuse. Retinal dehydrogenase appears to utilize a disordered loop in the substrate access channel to discriminate between retinaldehyde and short-chain aldehydes.
Related Citations: 
Cloning of a Cdna Encoding an Aldehyde Dehydrogenase and its Expression in Escherichia Coli. Recognition of Retinal as Substrate Wang, X.,Penzes, P.,Napoli, J.L. (1996) J.Biol.Chem. 271: 16288
Purification, Crystallization and Preliminary X-Ray Diffraction Studies of Retinal Dehydrogenase Type II Lamb, A.L.,Wang, X.,Napoli, J.L.,Newcomer, M.E. (1998) Acta Crystallogr.,Sect.D 54: 639
Restricted Expression and Retinoic Acid-Induced Downregulation of the Retinaldehyde Dehydrogenase Type 2 (Raldh-2) Gene During Mouse Development Niederreither, K.,Mccaffery, P.,Drager, U.C.,Chambon, P.,Dolle, P. (1997) Mech.Dev. 62: 67
Organizational Affiliation: 
Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, Tennessee 37232, USA.