lycopene beta-cyclase

{{Infobox enzyme

| Name = Lycopene β-cyclase

| EC_number = 5.5.1.19

| CAS_number = 220801-82-1

| GO_code =

| image =

| width =

| caption =

}}

Lycopene β-cyclase ({{EnzExplorer|5.5.1.19}}, CrtL, CrtL-b, CrtY) is an enzyme with systematic name carotenoid beta-end group lyase (decyclizing).{{cite journal | vauthors = Cunningham FX, Chamovitz D, Misawa N, Gantt E, Hirschberg J | title = Cloning and functional expression in Escherichia coli of a cyanobacterial gene for lycopene cyclase, the enzyme that catalyzes the biosynthesis of beta-carotene | journal = FEBS Letters | volume = 328 | issue = 1–2 | pages = 130–8 | date = August 1993 | pmid = 8344419 | doi = 10.1016/0014-5793(93)80980-9 | s2cid = 86704801 | authorlink2 = Daniel_Chamovitz | doi-access = free }}{{cite journal | vauthors = Cunningham FX, Sun Z, Chamovitz D, Hirschberg J, Gantt E | title = Molecular structure and enzymatic function of lycopene cyclase from the cyanobacterium Synechococcus sp strain PCC7942 | journal = The Plant Cell | volume = 6 | issue = 8 | pages = 1107–21 | date = August 1994 | pmid = 7919981 | pmc = 160505 | doi = 10.1105/tpc.6.8.1107 | jstor = 3869889 }}{{cite journal | vauthors = Hugueney P, Badillo A, Chen HC, Klein A, Hirschberg J, Camara B, Kuntz M | title = Metabolism of cyclic carotenoids: a model for the alteration of this biosynthetic pathway in Capsicum annuum chromoplasts | journal = The Plant Journal | volume = 8 | issue = 3 | pages = 417–24 | date = September 1995 | pmid = 7550379 | doi = 10.1046/j.1365-313x.1995.08030417.x | doi-access = free }}{{cite journal | vauthors = Pecker I, Gabbay R, Cunningham FX, Hirschberg J | title = Cloning and characterization of the cDNA for lycopene beta-cyclase from tomato reveals decrease in its expression during fruit ripening | journal = Plant Molecular Biology | volume = 30 | issue = 4 | pages = 807–19 | date = February 1996 | pmid = 8624411 | doi = 10.1007/bf00019013 | s2cid = 10470698 }}{{cite journal | vauthors = Hornero-Méndez D, Britton G | title = Involvement of NADPH in the cyclization reaction of carotenoid biosynthesis | journal = FEBS Letters | volume = 515 | issue = 1–3 | pages = 133–6 | date = March 2002 | pmid = 11943208 | doi = 10.1016/s0014-5793(02)02453-5 | s2cid = 25408239 }}{{cite journal | vauthors = Maresca JA, Graham JE, Wu M, Eisen JA, Bryant DA | title = Identification of a fourth family of lycopene cyclases in photosynthetic bacteria | journal = Proceedings of the National Academy of Sciences of the United States of America | volume = 104 | issue = 28 | pages = 11784–9 | date = July 2007 | pmid = 17606904 | pmc = 1905924 | doi = 10.1073/pnas.0702984104 | doi-access = free }} This enzyme catalyses the following chemical reaction

: carotenoid ψ-end group $\backslash rightleftharpoons$ carotenoid β-end group

This enzyme requires NAD(P)H. It converts Lycopene (2 ψ ends) into β-carotene (2 β ends).