All-trans-retinoic acid is a biologically active derivative of vitamin A that regulates numerous
physiological processes. The concentration of retinoic acid in the cells is tightly regulated,
but the exact mechanisms responsible for this regulation are not completely understood,
largely because the enzymes involved in the biosynthesis of retinoic acid have not been fully
defined. Recent studies using in vitro and in vivo models suggest that several members of
the short-chain dehydrogenase/reductase superfamily of proteins are essential for retinoic …