IUBMB Enzyme Nomenclature


Accepted name: lycopene β-cyclase

Reaction: carotenoid ψ-end group = carotenoid β-end group

For diagram of reaction click here, and here click here, and mechanism click here.

Other name(s): CrtL; CrtL-b; CrtY; LCYb; carotenoid β-end group lyase (decyclizing)

Systematic name: carotenoid β-end group lyase (ring-opening)

Comments: The enzyme is a non-redox flavoprotein, containing FADH2 that is used for stabilization of a transition state. Lycopene has a ψ-end group at both ends. When acting on one end, the enzyme forms γ-carotene. When acting on both ends it forms β-carotene. It also acts on neurosporene to give β-zeacarotene.

Links to other databases: BRENDA, EXPASY, KEGG, Metacyc, CAS registry number:


1. Cunningham, F.X., Jr., Chamovitz, D., Misawa, N., Gantt, E. and Hirschberg, J. Cloning and functional expression in Escherichia coli of a cyanobacterial gene for lycopene cyclase, the enzyme that catalyzes the biosynthesis of β-carotene. FEBS Lett. 328 (1993) 130-138. [PMID: 8344419]

2. Cunningham, F.X., Jr., Sun, Z., Chamovitz, D., Hirschberg, J. and Gantt, E. Molecular structure and enzymatic function of lycopene cyclase from the cyanobacterium Synechococcus sp strain PCC7942. Plant Cell 6 (1994) 1107-1121. [PMID: 7919981]

3. Hugueney, P., Badillo, A., Chen, H.C., Klein, A., Hirschberg, J., Camara, B. and Kuntz, M. Metabolism of cyclic carotenoids: a model for the alteration of this biosynthetic pathway in Capsicum annuum chromoplasts. Plant J. 8 (1995) 417-424. [PMID: 7550379]

4. Pecker, I., Gabbay, R., Cunningham, F.X., Jr. and Hirschberg, J. Cloning and characterization of the cDNA for lycopene β-cyclase from tomato reveals decrease in its expression during fruit ripening. Plant Mol. Biol. 30 (1996) 807-819. [PMID: 8624411]

5. Hornero-Mendez, D. and Britton, G. Involvement of NADPH in the cyclization reaction of carotenoid biosynthesis. FEBS Lett. 515 (2002) 133-136. [PMID: 11943208]

6. Maresca, J.A., Graham, J.E., Wu, M., Eisen, J.A. and Bryant, D.A. Identification of a fourth family of lycopene cyclases in photosynthetic bacteria. Proc. Natl. Acad. Sci. USA 104 (2007) 11784-11789. [PMID: 17606904]

7. Yu, Q., Schaub, P., Ghisla, S., Al-Babili, S., Krieger-Liszkay, A. and Beyer, P. The lycopene cyclase CrtY from Pantoea ananatis (formerly Erwinia uredovora) catalyzes an FADred-dependent non-redox reaction. J. Biol. Chem. 285 (2010) 12109-12120. [PMID: 20178989]

[EC created 2011]

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