Broad specificity mitochondrial dioxygenase that mediates the asymmetric oxidative cleavage of carotenoids (PubMed:16672231, PubMed:21081106). Cleaves carotenes (pure hydrocarbon carotenoids) such as all-trans-beta-carotene and lycopene as well as xanthophylls (oxygenated carotenoids) such as zeaxanthin, lutein and beta-cryptoxanthin at both the 9,10 and the 9',10' carbon-carbon double bond (PubMed:16672231, PubMed:21081106). Through its function in carotenoids metabolism regulates oxidative stress and the production of important signaling molecules (By similarity). all-trans-beta-carotene + O2 = all-trans-10'-apo-beta-carotenal + beta-ionone 5-cis-lycopene + O2 = (3E,5E)-6,10-dimethylundeca-3,5,9-trien-2-one + 5-cis-10'-apo-lycopenal 13-cis-lycopene + O2 = (3E,5E)-6,10-dimethylundeca-3,5,9-trien-2-one + 13-cis-10'-apo-lycopenal lutein + O2 = (3R)-3-hydroxy-10'-apo-beta-carotenal + (3R,6R)-hydroxy-alpha-ionone lutein + O2 = (3R)-hydroxy-beta-ionone + (3R,6R)-3-hydroxy-10'-apo-alpha-carotenal all-trans-zeaxanthin + 2 O2 = 2 (3R)-hydroxy-beta-ionone + 4,9-dimethyldodeca-2,4,6,8,10-pentaenedial all-trans-zeaxanthin + O2 = (3R)-3-hydroxy-10'-apo-beta-carotenal + (3R)-hydroxy-beta-ionone beta-cryptoxanthin + O2 = (3R)-hydroxy-beta-ionone + all-trans-10'-apo-beta-carotenal all-trans-10'-apo-beta-carotenal + O2 = 4,9-dimethyldodeca-2,4,6,8,10-pentaenedial + beta-ionone (3R)-3-hydroxy-10'-apo-beta-carotenal + O2 = (3R)-hydroxy-beta-ionone + 4,9-dimethyldodeca-2,4,6,8,10-pentaenedial (3R,6R)-3-hydroxy-10'-apo-alpha-carotenal + O2 = (3R,6R)-hydroxy-alpha-ionone + 4,9-dimethyldodeca-2,4,6,8,10-pentaenedial Binds 1 Fe(2+) ion per subunit. Optimum pH is 8.0-8.5 with all-trans-beta-carotene as substrate. Widely expressed. Detected in heart, spleen, lung, intestine, colon, stomach, kidney, bladder, and prostate. Highly expressed in liver and testis (at protein level). Up-regulated by lycopene. Belongs to the carotenoid oxygenase family.