Catalyzes the double cyclization reaction which converts lycopene to beta-carotene (PubMed:7919981, PubMed:8344419). It also converts neurosporene to the monocyclic beta-zeacarotene but does not cyclize zeta-carotene (PubMed:7919981). a carotenoid psi-end group = a carotenoid beta-end derivative all-trans-lycopene = gamma-carotene gamma-carotene = all-trans-beta-carotene all-trans-neurosporene = beta-zeacarotene Inhibited by the bleaching herbicide 2-(4-methylphenoxy)triethylamine hydrochloride (MPTA). Carotenoid biosynthesis; beta-carotene biosynthesis. Carotenoid biosynthesis; beta-zeacarotene biosynthesis. Belongs to the lycopene cyclase family.