A novel carotenoid biosynthetic route via oxidosqualene.

Over 800 known carotenoids are synthesized from phytoene or 4,4'-diapophytoene (dehydrosqualene) characterized by three conjugated double bonds. In this paper, we report that carotenoid desaturase CrtN from Staphylococcus aureus and Methylomonas can accept oxidosqualene, which is the precursor for plant- or animal-type triterpenoids, yielding the yellow carotenoid pigments with 8, 9, or 10 conjugated double bonds. The resulting pathway is the second nonnatural route for carotenoid pigments and the first pathway for carotenoid pigments not biosynthesized via (diapo)phytoene.