InterPro domain: IPR043205

Cytochrome b561 is a ferric-chelate reductase that reduces Fe3+ to Fe2+ before its transport from the endosome to the cytoplasm. It probably uses ascorbate as an electron donor [ 1 , 2 ].

Cytochrome b reductase 1 (CYBRD1) is an iron-regulated ferric reductase that catalyses the reduction of ferric to ferrous ion in the process of iron absorption in duodenal enterocytes [ 3 , 4 ]. 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) [ 5 ].

This entry represents a group of transmembrane reductases, including CYBRD1/CYB561/CYB561A3 from humans.CYB561A3 is a lysosomal membrane ascorbate-dependent ferrireductas.

1. An ascorbate-reducible cytochrome b561 is localized in macrophage lysosomes. Biochim. Biophys. Acta 1760, 1903-13
2. Three mammalian cytochromes b561 are ascorbate-dependent ferrireductases. FEBS J. 273, 3722-34
3. Modulation of Dcytb (Cybrd 1) expression and function by iron, dehydroascorbate and Hif-2α in cultured cells. Biochim. Biophys. Acta 1840, 106-12
4. The role of Dcytb in iron metabolism: an update. Biochem. Soc. Trans. 36, 1239-41