This enzyme is involved in carotenoid biosynthesis and catalyses up to three desaturation steps (cf. EC 1.3.99.29 [phytoene desaturase (¦Æ-carotene-forming)], EC 1.3.99.30 [phytoene desaturase (3,4-didehydrolycopene-forming)], EC 1.3.99.31 [phytoene desaturase (lycopene-forming)]). The enzyme is activated by FAD. NAD+, NADP+ or ATP show no activating effect [1].