Cytochrome b5 reductase

Cytochrome-b5 reductase is a NADH-dependent enzyme that converts ferricytochrome from a Fe3+ form to a Fe2+ form. It contains FAD and catalyzes the reaction:

NADH + H+ + 2 ferricytochrome b5 = NAD+ + 2 ferrocytochrome b5

cytochrome-b5 reductase
Ribbon diagram of erythrocytic methemoglobin reductase with FAD bound. From PDB: 1UMK.
Identifiers
EC number1.6.2.2
CAS number9032-25-1
Databases
IntEnzIntEnz view
BRENDABRENDA entry
ExPASyNiceZyme view
KEGGKEGG entry
MetaCycmetabolic pathway
PRIAMprofile
PDB structuresRCSB PDB PDBe PDBsum
Gene OntologyAmiGO / QuickGO
Cytochrome b5 reductase
Identifiers
SymbolCYB5R
InterProIPR001834
Membranome421

In its b5-reducing capacity, this enzyme is involved in desaturation and elongation of fatty acids, cholesterol biosynthesis, and drug metabolism.

This enzyme can also reduce methemoglobin to normal hemoglobin, gaining it the inaccurate synonym methemoglobin reductase. Isoforms expressed in erythrocytes (CYB5R1, CYB5R3) perform this function in vivo. Ferricyanide is another substrate in vitro.

The following four human genes encode cytochrome-b5 reductases:

See also

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