biostudies-literatureHarrison EHNational Institutes of HealthNIH HHS1411https://www.ebi.ac.uk/biostudies/studies/S-EPMC9003029biostudies-literatureUnknown14(7)Naturally occurring retinoids (retinol, retinal, retinoic acid, retinyl esters) are a subclass of β-apocarotenoids, defined by the length of the polyene side chain. Provitamin A carotenoids are metabolically converted to retinal (β-apo-15-carotenal) by the enzyme β-carotene-15,15'-dioxygenase (BCO1) that catalyzes the oxidative cleavage of the central C=C double bond. A second enzyme β-carotene-9'-10'-dioxygenase cleaves the 9',10' bond to yield β-apo-10'-carotenal and β-ionone. Chemical oxidation of the other double bonds leads to the generation of other β-apocarotenals. Like retinal, some of these β-apocarotenals are metabolically oxidized to the corresponding β-apocarotenoic acids or reduced to the β-apocarotenols, which in turn are esterified to β-apocarotenyl esters. Other metabolic fNutrientsCarotenoids, β-Apocarotenoids, and Retinoids: The Long and the Short of It.PMC9003029R01-DK055598, R01-DK10151, R01-HL04987Harrison EHfalseCarotenoids, β-Apocarotenoids, and Retinoids: The Long and the Short of It.Naturally occurring retinoids (retinol, retinal, retinoic acid, retinyl esters) are a subclass of β-apocarotenoids, defined by the length of the polyene side chain. Provitamin A carotenoids are metabolically converted to retinal (β-apo-15-carotenal) by the enzyme β-carotene-15,15'-dioxygenase (BCO1) that catalyzes the oxidative cleavage of the central C=C double bond. A second enzyme β-carotene-9'-10'-dioxygenase cleaves the 9',10' bond to yield β-apo-10'-carotenal and β-ionone. Chemical oxidation of the other double bonds leads to the generation of other β-apocarotenals. Like retinal, some of these β-apocarotenals are metabolically oxidized to the corresponding β-apocarotenoic acids or reduced to the β-apocarotenols, which in turn are esterified to β-apocarotenyl esters. Other metabolic f2022-01-01T00:00:00Z2022 Mar2025-04-19T12:12:06.507Z2024-10-19T06:51:33.354ZS-EPMC90030293540602410.3390/nu14071411