DcytB

DCYTB, short for duodenal cytochrome b, is a membrane-bound ferric reductase that plays a key role in dietary iron absorption. In humans it is encoded by the CYBRD1 gene and is commonly referred to as duodenal cytochrome b (Dcytb). It belongs to the cytochrome b561 family of electron transport proteins and functions as an ascorbate-dependent ferrireductase.

In the intestinal mucosa, Dcytb is located at the apical (brush-border) membrane of enterocytes in the duodenum and upper jejunum. It catalyzes the two-electron reduction of ferric iron (Fe3+) to ferrous iron (Fe2+) using electrons donated by luminal ascorbate (vitamin C). The produced Fe2+ is then transported into enterocytes by the iron transporter DMT1 (SLC11A2) for systemic distribution, with basolateral export by ferroportin to the circulation.

Beyond the duodenum, CYBRD1 transcripts have been detected in other tissues, including placenta and liver, suggesting broader roles in cellular iron handling and ferrireductase activity under certain physiological conditions. Dcytb’s membership in the cytochrome b561 family reflects its general mechanism of mediating ascorbate-driven electron transfer across membranes.

Expression of Dcytb is responsive to iron status; iron deficiency tends to upregulate its expression, while iron sufficiency represses it, adjusting iron uptake capacity. The protein’s activity depends on adequate vitamin C levels, as ascorbate deficiency can impair iron absorption. Disturbances in Dcytb function can contribute to impaired iron uptake and iron-related disorders.

See also: DMT1, ferroportin, hephaestin, iron metabolism.