Oxidoreductase that plays a key role in early steps of protein N-linked glycosylation by mediating two non-consecutive steps in dolichol biosynthesis (PubMed:38821050). Acts both as a NAD(+)- dependent dehydrogenase and as a NADPH-dependent reductase during the conversion of polyprenol into dolichol (PubMed:38821050). First catalyzes the NAD(+)-dependent dehydrogenation of polyprenol into polyprenal; polyprenal is then reduced into dolichal by SRD5A3 (PubMed:38821050). It then catalyzes the NADPH-dependent reduction of dolichal into dolichol (PubMed:38821050). May also acts as a positive regulator of starvation-induced autophagy (PubMed:25076851). . This is the function of ENSG00000169084 (DHRSX, dehydrogenase/reductase X-linked).