CYBRD1 (cytochrome b reductase 1), also known as duodenal cytochrome b (Dcytb), is an iron-regulated ferric reductase catalyses the reduction of ferric to ferrous ion in the process of iron absorption in duodenal enterocytes [, ]. It shares protein sequence similarity with cytochrome b561, an enzyme involved in the regeneration of ascorbic acid (AA) from semi dehydroascorbic acid (DHA) or ascorbate free radical (AFR) []. The expression of Dcytb is induced by modulators for iron absorption, such as Hif-2alpha []. It is a plasma membrane reductase that uses cytoplasmic ascorbate as an electron donor to reduce extracellular Fe3+ into Fe2+ []. It functions in dietary iron absorption at the brush border of duodenal enterocytes by producing Fe2+, the divalent form of iron that can be transported into enterocytes []. It is also able to reduce extracellular monodehydro-L-ascorbate and may be involved in extracellular ascorbate regeneration by erythrocytes in blood [].
