Figure 1.

Scheme for the proposed metabolism of β-carotene. β-Carotene is cleaved symmetrically by BCO1 in the cytoplasm to two molecules of retinal. Retinal can be converted to biologically active retinoic acid to serve as a gene regulator or to retinol for distribution throughout the body. BCO2, cleaves β,β-carotene asymmetrically at the 9′,10′ position generating β-apo-10′-carotenal (Apo10al) and β-ionone. β-apo-8′-carotenal(Apo8al) and β-apo-12′-carotenal(Apo12al) have also been implicated as products of BCO2 mediated cleavage.