Carotenoid dioxygenase; part of the car gene cluster that mediates the biosynthesis of neurosporaxanthin, a carboxylic apocarotenoid acting as an essential protective pigments and leading to orange pigmentation. CarX mediates the cleavage of beta-carotene produced by carAR into retinal, the rhodopsin's chromophore that is involved in the regulation of the carotenoid biosynthetic pathway via a negative feedback mechanism. It can also convert the synthetic compound beta-apo-8'-carotenal but not C35-apocarotenoids such as the acidic apocarotenoid neurosporaxanthin (C35), as well as its corresponding aldehyde beta-apo-4'-carotenal