Catalyzes the double cyclization reaction which converts lycopene to beta-carotene and neurosporene to beta-zeacarotene. a carotenoid psi-end group = a carotenoid beta-end derivative Carotenoid biosynthesis; beta-carotene biosynthesis. Carotenoid biosynthesis; beta-zeacarotene biosynthesis. Exists as an inactive soluble form and an active membrane-bound form. Belongs to the lycopene cyclase family.