Cytochrome b5 reductase (null)

Cytochrome b5 reductase is an oxidoreductase enzyme present in all cells but primarily functionally important in erythrocytes, where it is also known as "methemoglobin reductase." Its main physiological role in red blood cells is to catalyze the reduction of methemoglobin (Fe^3+) to functional hemoglobin (Fe^2+) using electrons from NADH. This process is essential for maintaining the oxygen-carrying capacity of blood by limiting the accumulation of methemoglobin, which cannot bind oxygen. Deficiency in cytochrome b5 reductase activity results in methemoglobinemia, a condition characterized by impaired oxygen delivery and cyanosis. While cytochrome b5 reductase has critical roles in lipid metabolism across tissues, its "methemoglobin reductase" function is vital in erythrocytes[1][3][4].

Other names

Methemoglobin reductaseNADH-cytochrome b5 reductaseDiaphorase 1CYB5RB5R

Methylene blue acts by accepting electrons from NADPH and promoting reduction of methemoglobin (via NADPH-methemoglobin reductase pathway)[3][4] Ascorbic acid and glutathione act as non-enzymatic reducing agents for methemoglobin[3]