Dehydrogenates carotenes in the trans conformation: converts all-trans-zeta-carotene into all-trans-lycopene, one of the last dehydrogenation steps of lycopene biosynthesis. 2 A + all-trans-zeta-carotene = 2 AH2 + all-trans-lycopene Carotenoid biosynthesis; lycopene biosynthesis. By blue light. Belongs to the carotenoid/retinoid oxidoreductase family.