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Beta-carotene 15,15'-monooxygenase

In enzymology, β-carotene 15,15'-monooxygenase (EC is an enzyme that catalyzes the biological reaction

β-carotene 15,15'-monooxygenase
EC number
CAS number 37256-60-3
IntEnz IntEnz view
ExPASy NiceZyme view
MetaCyc metabolic pathway
PRIAM profile
PDB structures RCSB PDB PDBe PDBsum
Gene Ontology AmiGO / QuickGO
β-carotene + O2 → 2retinal

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.[1]

This enzyme belongs to the family of oxidoreductases, specifically those acting on paired donors, with O2 as oxidant and incorporation or reduction of oxygen. The systematic name of this enzyme class is β-carotene:oxygen 15,15'-oxidoreductase (bond-cleaving). Other names in common use include β-carotene 15,15'-dioxygenase and β-carotene dioxygenase.

In general, carnivores are poor converters of ionone-containing carotenoids, and pure carnivores such as cats and ferrets lack 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.


  1. ^ "beta-Carotene 15,15'-Dioxygenase activity in human tissues and cells: evidence of an iron dependency". J Nutr Biochem. 12 (11): 640–647. Nov 2001. doi:10.1016/s0955-2863(01)00184-x. PMID 12031257. 
  • Leuenberger MG, Engeloch-Jarret C & Woggon WD (2001). "The reaction mechanism of the enzyme-catalysed central cleavage of beta-carotene to retinal". Angew. Chem. 40: 2614–2616. doi:10.1002/1521-3773(20010716)40:14<2613::aid-anie2613>;2-z. 
  • Goodman DS, Huang HS, Kanai M & Shiratori T (1967). "The enzymatic conversion of all-trans beta-carotene into retinal". J. Biol. Chem. 242: 3543–3554. 
  • Goodman DS, Huang HS, Shiratori T (1966). "Mechanism of the biosynthesis of vitamin A from beta-carotene". J. Biol. Chem. 241 (9): 1929–32. PMID 5946623.