Reaction: β-carotene + O2 = 2 all-trans-retinal (overall reaction)
(1a) β-carotene + O2 + AH2 = β-carotene 15,15'-epoxide + H2O + A
(1b) β-carotene 15,15'-epoxide + H2O = 15,15'-dihydroxy-β-carotene
(1c) 15,15'-dihydroxy-β-carotene + A = 2 all-trans-retinal + AH2
For diagram of reaction click here and mechanism click here.
Other name(s): β-carotene 15,15'-dioxygenase (misleading); carotene dioxygenase (misleading); carotene 15,15'-dioxygenase (misleading); BCMO1 (gene name); BCDO (misleading)
Systematic name: β-carotene:oxygen 15,15'-oxidoreductase (15,15'-epoxidizing, bond-cleaving)
Comments: Requires bile salts and Fe(II). This animal enzyme catalyses the reaction in three stages, epoxidation of the 15,15'-double bond, hydration of the epoxide leading to ring opening, and oxidative cleavage of the diol formed. Thus only one atom of the dioxygen is incorporated into each retinal molecule. The nature of the acceptor listed in reactions (1a) and (1c) is assumed to be iron within the active site. Formerly classified in EC 1.13.11 as it had been thought to be a dioxygenase. cf. EC 18.104.22.168, β-carotene 15,15'-dioxygenase.
Links to other databases: BRENDA, EXPASY, KEGG, Metacyc, CAS registry number: 37256-60-3
1. Goodman, D.S., Huang, H.S. and Shiratori, T. Mechanism of the biosynthesis of vitamin A from β-carotene. J. Biol. Chem. 241 (1966) 1929-1932. [PMID: 5946623]
2. Goodman, D.S., Huang, H.S., Kanai, M. and Shiratori, T. The enzymatic conversion of all-trans β-carotene into retinal. J. Biol. Chem. 242 (1967) 3543-3554.
3. Leuenberger, M.G., Engeloch-Jarret, C. and Woggon, W.D. The reaction mechanism of the enzyme-catalysed central cleavage of β-carotene to retinal. Angew. Chem. Int. Ed. 40 (2001) 2614-2616. [PMID: 11458349]
4. Kim, Y.S. and Oh, D.K. Substrate specificity of a recombinant chicken β-carotene 15,15'-monooxygenase that converts β-carotene into retinal. Biotechnol. Lett. 31 (2009) 403–408. [PMID: 18979213]