Beta-carotene 15,15'-dioxygenase
In enzymology, β-carotene 15,15'-dioxygenase is an enzyme with systematic name beta-carotene:oxygen 15,15'-dioxygenase . In human it is encoded by the BCO1 gene. This enzyme catalyses the following chemical reaction
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. It can also cleave beta-cryptoxanthin, apocarotenal, 4'-apo-β-carotenal, alpha-carotene and γ-carotene in decreasing order, all substrates greater than C30 with at least one unsubstituted β-ionone ring.
This enzyme belongs to the family of oxidoreductases, specifically those acting on paired donors, with O2 as oxidant and incorporation or reduction of oxygen. Other names in common use include β-carotene 15,15'-monooxygenase and β-carotene dioxygenase. Its previous EC numbers include 1.13.11.21, 1.14.99.36.
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. They must have preformed vitamin A in their diet.
Beta-carotene 15,15'-dioxygenase contains Fe2+.
