BCMO1

BCMO1, or beta-carotene 15,15'-monooxygenase 1, is a human gene that encodes an enzyme responsible for the first step in converting provitamin A carotenoids into vitamin A. The encoded enzyme is a carotenoid oxygenase that cleaves all-trans-beta-carotene at the central 15,15' double bond, yielding two molecules of retinal (retinaldehyde). Retinal can be reduced to retinol (vitamin A) or oxidized further to retinoic acid, which acts as a signaling molecule.

Expression and function: BCMO1 is expressed mainly in the small intestine, the primary site of dietary carotenoid processing, and is also found in liver and other tissues with roles in carotenoid metabolism. Its activity determines how efficiently dietary beta-carotene contributes to vitamin A status; individuals with higher BCMO1 activity typically convert beta-carotene more readily to retinol.

Genetic variation: The BCMO1 gene exhibits genetic polymorphisms that influence catalytic efficiency. Common variants can alter conversion efficiency, affecting plasma levels of beta-carotene and retinol after carotenoid intake. Population studies show substantial interindividual and interethnic variation in provitamin A conversion linked to BCMO1 haplotypes.

Clinical and nutritional implications: Variation in BCMO1 activity contributes to variability in vitamin A status among people consuming provitamin A–rich foods or supplements. In contexts of dietary restriction or malnutrition, reduced conversion efficiency can exacerbate vitamin A deficiency risk. Conversely, higher BCMO1 activity can increase accumulation of beta-carotene in plasma without proportionate retinol increase.

Research and regulation: BCMO1 remains a focus of nutrigenomics and metabolic research, informing dietary recommendations and understanding of carotenoid bioavailability. Further studies clarify how genetic variation interacts with diet to influence vitamin A homeostasis.