Recombinant class I aldehyde dehydrogenases specific for all-trans- or 9-cis-retinal.

The molecular basis for the specificity of aldehyde dehydrogenases (ALDHs) for retinal, the precursor of the morphogen retinoic acid, is still poorly understood. We have expressed in Escherichia coli both retinal dehydrogenase (RALDH), a cytosolic aldehyde dehydrogenase originally isolated from rat kidney, and the highly homologous phenobarbital-induced aldehyde dehydrogenase (PB-ALDH). Oxidation of propanal was observed with both enzymes.