This family consists of lycopene beta and epsilon cyclase proteins. Carotenoids with cyclic end groups are essential components of the photosynthetic membranes in all plants, algae, and cyanobacteria. These lipid-soluble compounds protect against photo-oxidation, harvest light for photosynthesis, and dissipate excess light energy absorbed by the antenna pigments. The cyclisation of lycopene (psi, psi-carotene) is a key branch point in the pathway of carotenoid biosynthesis. Two types of cyclic end groups are found in higher plant carotenoids: the beta and epsilon rings. Carotenoids with two beta rings are ubiquitous, and those with one beta and one epsilon ring are common; however, carotenoids with two epsilon rings are rare [1,2].

1: Functional analysis of the beta and epsilon lycopene cyclase enzymes of Arabidopsis reveals a mechanism for control of cyclic carotenoid formation. Cunningham FX Jr, Pogson B, Sun Z, McDonald KA, DellaPenna D, Gantt E; Plant Cell 1996;8:1613-1626. PMID:8837512

2: One ring or two? Determination of ring number in carotenoids by lycopene epsilon-cyclases. Cunningham FX Jr, Gantt E; Proc Natl Acad Sci U S A 2001;98:2905-2910. PMID:11226339