therefore , carotenoid cyclization in m. roseus does not involve neurosporene or lycopene and must occur early in carotene biosynthesis , prior to the formation of beta-zeacarotene , zeta-carotene is proposed as the cyclization substrate and beta-zeacarotene as the substrate for oxygen insertion .
C0007271
carotenoid
C0043470
zeta-carotene