Beta-carotene 15,15'-dioxygenase

BCO1
Identifiers
Aliases	BCO1, BCDO, BCDO1, BCMO, BCMO1, BCO, beta-carotene oxygenase 1
External IDs	OMIM: 605748 MGI: 1926923 HomoloGene: 41172 GeneCards: BCO1
EC number	1.13.11.63
Gene location (Human) Chr. Chromosome 16 (human)[1] Band 16q23.2 Start 81,238,689 bp[1] End 81,291,142 bp[1]
Gene location (Mouse) Chr. Chromosome 8 (mouse)[2] Band 8|8 E1 Start 117,822,593 bp[2] End 117,860,459 bp[2]
RNA expression pattern Bgee Human Mouse (ortholog) Top expressed in retinal pigment epithelium jejunal mucosa duodenum palpebral conjunctiva rectum pancreatic ductal cell gallbladder islet of Langerhans kidney kidney tubule Top expressed in yolk sac seminiferous tubule intestinal villus hepatobiliary system liver spermatid hair follicle islet of Langerhans jejunum pineal gland More reference expression data BioGPS n/a
Gene ontology Molecular function oxidoreductase activity beta-carotene 15,15'-dioxygenase activity oxidoreductase activity, acting on single donors with incorporation of molecular oxygen, incorporation of two atoms of oxygen dioxygenase activity metal ion binding retinal isomerase activity carotenoid dioxygenase activity Cellular component cytosol Biological process retinol metabolic process vitamin A biosynthetic process retinoid metabolic process retinal metabolic process beta-carotene metabolic process carotene catabolic process Sources:Amigo / QuickGO
Orthologs Species Human Mouse Entrez 53630 63857 Ensembl ENSG00000135697 ENSMUSG00000031845 UniProt Q9HAY6 Q9JJS6 RefSeq (mRNA) NM_017429 NM_001163028 NM_021486 RefSeq (protein) NP_059125 NP_001156500 NP_067461 Location (UCSC) Chr 16: 81.24 – 81.29 Mb Chr 8: 117.82 – 117.86 Mb PubMed search [3] [4]
Wikidata
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In enzymology, beta-carotene 15,15'-dioxygenase, (EC 1.13.11.63) is an enzyme with systematic name beta-carotene:oxygen 15,15'-dioxygenase (bond-cleaving).^[5][6] In human it is encoded by the BCO1 gene. This enzyme catalyses the following chemical reaction

beta-carotene + O₂ → 2 all-trans-retinal

This is a cleavage reaction which cleaves β-carotene, utilizes molecular oxygen, is enhanced by the presence of bile salts and thyroxine, and generates two molecules of retinal. In humans, the enzyme is present in the small intestine and liver.^[7] The dioxygenase also asymmetrically cleaves beta-cryptoxanthin, trans-β-apo-8'-carotenal, beta-4'-apo-β-carotenal, alpha-carotene and gamma-carotene in decreasing order, creating one retinal molecule, all of these being substrates with a carbon chain greater than C₃₀, with at least one unsubstituted β-ionone ring.^[8]

This enzyme belongs to the (enzymatically-defined) family of oxidoreductases, specifically those acting on paired donors, with O₂ as oxidant and incorporation or reduction of oxygen. A related enzyme is β-carotene 15,15'-monooxygenase, coded for by the gene BCMO1, which symmetrically cleaves β-carotene into two retinal molecules.^[9][10]

In general, carnivores are poor converters of ionone-containing carotenoids, and pure carnivores such as felids (cats) lack beta-carotene 15,15'-dioxygenase and beta-carotene 15,15'-monooxygenase and cannot convert any carotenoids to retinal, resulting in none of the carotenoids being forms of vitamin A for these species. They must have preformed vitamin A in their diet.^[11]

Beta-carotene 15,15'-dioxygenase belongs to the (similarity-defined) family of carotenoid oxygenases (InterPro: IPR004294). Enzymes of this family contain a Fe²⁺ active site, coordinated usually by four His residues.^{[citation needed]}

References