Cytochrome b5 reductase

Cytochrome b5 reductase (CBR, B5R ), more NADH - cytochrome b5 reductase, formerly methemoglobin reductase enzymes in mammals, the trivalent reduction of the bound to the protein cytochrome b5 heme with the complexed iron ion from divalent are in the catalyze state. NADH is oxidized at the same time by removing two electrons to NAD , and H . This redox reaction is essential for reduction of methemoglobin, the recycling of ascorbate, in the lipid metabolism, and more generally in the transfer of electrons from NADH to other substrates. Mutations in CYB5R3 gene responsible for hereditary methemoglobinemia.

Structurally and functionally related are the B5R enzymes with NAD ( P) H: nitrate reductases in plants and fungi. Both families belong to the superfamily of flavoprotein pyridine nucleotide cytochrome reductases, which occur in eukaryotes and bacteria.

In humans there are five paralogous cytochrome b5 reductase genes can still form in each case a plurality of different enzymes by alternative splicing: