BCO1 (beta-carotene oxygenase 1) is the primary enzyme responsible for converting provitamin A carotenoids to vitamin A in mammals. The enzyme catalyzes the symmetric cleavage of β-carotene at the central 15,15' carbon-carbon double bond through a dioxygenase mechanism, producing two molecules of retinaldehyde (retinal) 1. BCO1 utilizes molecular oxygen to cleave not only β-carotene but also β-apocarotenals and lycopene, with the iron cofactor forming an octahedral coordination sphere with four conserved histidine residues 12. The enzyme is highly expressed in liver and intestine, with cellular localization in hepatocytes, hepatic stellate cells, portal endothelial cells, and mucosal epithelium, where it resides in the cytosol 3. BCO1 activity is crucial for whole-body carotenoid and vitamin A homeostasis and influences lipid metabolism and energy balance 1. Common genetic polymorphisms, such as rs6564851, significantly affect circulating β-carotene levels and carotenoid metabolism 4. BCO1 deficiency is associated with hypercarotenemia and vitamin A deficiency, and therapeutic overexpression in adipose tissue has shown promise for reducing obesity through local vitamin A production 5.