Requires Fe2+. The enzyme cleaves beta-carotene symmetrically, producing two molecules of all-trans-retinal. Both atoms of the oxygen molecule are incorporated into the products . The enzyme can also process beta-cryptoxanthin, 8'-apo-beta-carotenal, 4'-apo-beta-carotenal, alpha-carotene and gamma-carotene in decreasing order. The presence of at least one unsubstituted beta-ionone ring in a substrate greater than C(30) is mandatory . A prokaryotic enzyme has been reported from the uncultured marine bacterium 66A03, where it is involved in the proteorhodopsin system, which uses retinal as its chromophore [6,7].