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Cytochrome b5 reductase 3
Protein CYB5R3 PDB 1ndh.png
PDB rendering based on 1ndh.
Available structures
PDB Ortholog search: PDBe, RCSB
Symbols CYB5R3 ; B5R; DIA1
External IDs OMIM613213 MGI94893 HomoloGene47921 ChEMBL: 2146 GeneCards: CYB5R3 Gene
EC number
RNA expression pattern
PBB GE CYB5R3 201885 s at tn.png
More reference expression data
Species Human Mouse
Entrez 1727 109754
Ensembl ENSG00000100243 ENSMUSG00000018042
UniProt P00387 Q9DCN2
RefSeq (mRNA) NM_000398 NM_029787
RefSeq (protein) NP_000389 NP_084063
Location (UCSC) Chr 22:
43.01 – 43.05 Mb
Chr 15:
83.15 – 83.17 Mb
PubMed search [1] [2]

NADH-cytochrome b5 reductase 3 is an enzyme that in humans is encoded by the CYB5R3 gene.[1][2]

Two forms of NADH-cytochrome b5 reductase are known, a membrane-bound form in somatic cells (anchored in the endoplasmic reticulum, mitochondrial and other membranes) and a soluble form in erythrocytes. The former exists mainly on the cytoplasmic side of the endoplasmic reticulum and functions in desaturation and elongation of fatty acids, in cholesterol biosynthesis, and in drug metabolism. The erythrocyte form is located in a soluble fraction of circulating erythrocytes and is involved in methemoglobin reduction. The membrane-bound form has both membrane-binding and catalytic domains. The soluble form has only the catalytic domain. This gene encodes both forms of the enzyme which arise from tissue-specific alternative transcripts that differ in the first exon. Mutations in this gene cause methemoglobinemias.[3]


  1. ^ Tomatsu S, Kobayashi Y, Fukumaki Y, Yubisui T, Orii T, Sakaki Y (Dec 1989). "The organization and the complete nucleotide sequence of the human NADH-cytochrome b5 reductase gene". Gene 80 (2): 353–61. doi:10.1016/0378-1119(89)90299-0. PMID 2479590. 
  2. ^ Bull PC, Shephard EA, Povey S, Santisteban I, Phillips IR (Nov 1989). "Cloning and chromosomal mapping of human cytochrome b5 reductase (DIA1)". Ann Hum Genet 52 (Pt 4): 263–8. doi:10.1111/j.1469-1809.1988.tb01105.x. PMID 3268037. 
  3. ^ "Entrez Gene: CYB5R3 cytochrome b5 reductase 3". 

Further reading[edit]