Cytochrome b5 reductases
Cytochrome b5 reductases | ||
---|---|---|
Ribbon model of the soluble isoform of B5R3 (methaemoglobin reductase), with FAD as domes, according to PDB 1UMK | ||
Mass / length primary structure | differently | |
Cofactor | FAD | |
Identifier | ||
Gene name (s) | CYB5R1 , CYB5R2 , CYB5R3 , CYB5R4 , CYB5RL | |
Enzyme classification | ||
EC, category | 1.6.2.2 , oxidoreductase | |
Response type | Redox reaction | |
Substrate | NADH + Fe 3+ cytochrome b5 | |
Products | NAD + + H + + Fe 2+ cytochrome b5 | |
Occurrence | ||
Parent taxon | Mammals |
Cytochrome b 5 reductases (CBR, B5R) , more specifically NADH-cytochrome b 5 reductase, formerly methemoglobin reductase, are enzymes in mammals , the reduction of to the protein cytochrome b 5 bound heme with the complexed iron - Ion from trivalent catalyze into the divalent state . At the same time, NADH is oxidized to NAD + and H + by withdrawing 2 electrons . This redox reaction is essential for the reduction of methemoglobin , the recycling of ascorbate , in lipid metabolism , and in general for the transfer of electrons from NADH to other substrates. Mutations in CYB5R3 - gene are responsible for hereditary methemoglobinemia responsible.
The B5R enzymes are structurally and functionally related to the NAD (P) H: nitrate reductases in plants and fungi. Both families belong to the superfamily of flavoprotein pyridine nucleotide cytochrome reductases , which are found in eukaryotes and bacteria .
In humans there are five paralogous cytochrome b 5 reductase genes , each of which can form several different enzymes through alternative splicing :
Gene name |
protein | OMIM | variants | size | comment |
---|---|---|---|---|---|
CYB5R1 | Q9UHQ9 | 608341 | 1 | 305 | single pass membrane protein ( nucleolus ); widely expressed |
CYB5R2 | Q6BCY4 | 608342 | 2 | 276 | not expressed everywhere; responsible for lucigenin chemiluminescence |
CYB5R3 | P00387 | 250800 | M / S | 300/ 275 |
Membrane protein (M, endoplasmic reticulum and mitochondrion ) and soluble isoform (S, methemoglobin reductase ); S only expressed in erythrocytes , responsible for type I methaemoglobinemia . |
CYB5R4 | Q7L1T6 | 608343 | 1 | 521 | soluble; endoplasmic reticulum; widely expressed; protects the pancreas from oxidative stress |
CYB5RL | Q6IPT4 | 3 | 314/ 167/ 247 |
Individual evidence
Web links
- D'Eustachio / reactome: Reduction of ferric cytochrome B5A to ferrous cytochrome B5A