carotenoid biosynthesis GO:0016117 pathway UPa:UPA00386 Biosynthesis of carotenoids, a group of essential photoprotective and antioxidant pigments that are naturally occurring in plants and some other photosynthetic organisms like algae, some types of fungus and some bacteria. There are over 600 known carotenoids; they are split into two classes, xanthophylls and carotenes. The most important function of carotenoid pigments, especially beta-carotene in higher plants, is to protect organisms against photooxidative damage. Carotenoid biosynthesis involves a series of desaturations, cyclizations, hydroxylations and epoxydations commencing with the formation of phytoene. PMID:11884677 isoprenoid biosynthesis pigment biosynthesis