Phytoene desaturase involved in the carotenoid biosynthesis pathway. Converts phytoene into 3,4-didehydrolycopene via the intermediary of phytofluene, zeta-carotene, neurosporene and lycopene, by introducing up to five double bonds into phytoene (By similarity). 15-cis-phytoene + 5 A = 5 AH2 + all-trans-3,4-didehydrolycopene Carotenoid biosynthesis; lycopene biosynthesis. Belongs to the carotenoid/retinoid oxidoreductase family.