Duodenal cytochrome B (Dcytb) has been identified as the reductase enzyme which catalyzes the reduction of Fe3+ to Fe2+ in the process of iron absorption in the duodenum of mammals. According to research carried out, it appears that Dcytb upregulation is controlled by a number of independent stimulators or inhibitors of iron absorption. Furthermore, Dcytb has also been shown to exist in other tissues besides the apical region of the duodenum; and as such, it is believed to play a major role in iron metabolism in tissues.
^Latunde-Dada GO, Van der Westhuizen J, Vulpe CD et al. (2002). "Molecular and functional roles of duodenal cytochrome B (Dcytb) in iron metabolism". Blood Cells Mol. Dis.29 (3): 356–60. doi:10.1006/bcmd.2002.0574. PMID12547225.CS1 maint: Explicit use of et al. (link)