The reaction occurs in the reverse direction with reduction of the terminal double bond next to the alcohol group. Isolated from human fetal brain tissue but present in all eukaryotes. In mammalian cells dolichols are predominantly 18-21 isoprene units in length.
enzyme is necessary for the reduction of the alpha-isoprene unit of polyprenols to form dolichols, required for synthesis of dolichol-linked monosaccharides and the oligosaccharide precursor used for N-glycosylation
the activities of yeast cis-prenyltransferases Rer2p and Srt1p and polyprenol reductase are not co-regulated and the reductase may be the rate-limiting enzyme in dolichol synthesis if the amount of polyisoprenoids synthesized exceeds a certain level
loss of function mutations of the SRD5A3 gene cause a multisystemic syndrome with eye malformations, cerebellar vermis hypoplasia, and psychomotor delay. Plasma from patients shows increased level of polyprenoids