<p>Phytoene dehydrogenase (phytoene desaturase) is an enzyme of carotenoidbiosynthesis that converts phytoene into zeta-carotene via the symmetricalintroduction of two double bonds at the C-11 and C-11' positions of phytoene.The sequence of phytoene dehydrogenase from bacteria (gene crtI or carC) andfungi (gene AL-1) are not related to that from cyanobacteria and plants but areevolutionary related [<cite idref="PUB00002578"/>] to that of another enzyme of carotenoid biosynthesis,methoxyneurosporene dehydrogenase (gene crtD).There are two glycine-rich conserved regions, both of which probably play arole in the binding of either FAD or NAD. The first conserved region is in theN-terminal section while the second one is in the C-terminal section.</p> Phytoene dehydrogenase, bacterial-type, conserved site