Based on limited published evidence, CYB561D1 is a transmembrane reductase belonging to the cytochrome b561 family. It contains two heme-b redox centers and functions as an integral membrane protein with six transmembrane domains 1. The protein likely uses ascorbate as an electron donor to transfer electrons across membranes, reducing monodehydro-L-ascorbate radicals and Fe(3+) cations in different cellular compartments. CYB561D1 localizes to the endoplasmic reticulum membrane and exhibits oxidoreductase activity. While structural and spectroscopic properties have been characterized, its specific physiological role remains incompletely understood.