Bifunctional enzyme that catalyzes the reactions from geranylgeranyl diphosphate to phytoene (phytoene synthase) and from lycopene to beta-carotene via the intermediate gamma-carotene and from 3,4-didehydrolycopene to torulene (lycopene cyclase). Torulene is further processed to the acidic carotenoid neurosporaxanthin. The cyclase preferentially catalyzes single cyclizations at only one end of the substrate to produce monocyclic carotenoids. all-trans-lycopene = gamma-carotene gamma-carotene = all-trans-beta-carotene 2 (2E,6E,10E)-geranylgeranyl diphosphate = 15-cis-phytoene + 2 diphosphate Carotenoid biosynthesis; beta-carotene biosynthesis. Carotenoid biosynthesis; phytoene biosynthesis; all-trans-phytoene from geranylgeranyl diphosphate: step 1/1. By blue light. In the N-terminal section; belongs to the lycopene beta-cyclase family. In the C-terminal section; belongs to the phytoene/squalene synthase family.