1-Hydroxycarotenoid 3,4-desaturase (EC1.3.99.27, CrtD, hydroxyneurosporene desaturase, carotenoid 3,4-dehydrogenase, 1-hydroxy-carotenoid 3,4-dehydrogenase) is an enzyme with systematic name1-hydroxy-1,2-dihydrolycopene:acceptor oxidoreductase.[1][2][3] This enzyme catalyses the following chemical reaction