A Novel Lycopene β‑Cyclase from Crocus Sativus with Comparable Activity in Carotenoid Biosynthesis

Lycopene cyclase (LCY) plays a central role in branching
the formation
of α-type or β-type carotene. In this study, a novel lycopene
cyclase (CsLcyB3) was identified from the full-length
transcriptome of Crocus sativus, the
major natural source of crocin with high economic value. Bioinformatic
analysis revealed that CsLcyB3 had the classic features of lycopene
cyclase and shared 38.85–92.39% identity with recorded functional
LCYs from C. sativus. Phylogenetic
analysis revealed that CsLcyB3 was grouped with LcyB-type LCYs from
higher plants and algae, suggesting its function in cyclizing lycopene
to form β-carotene, which was further confirmed by subsequent
functional complementation assays. The physicochemical features and
3D structure were also analyzed, attempting to explain the differences
in catalytic activity among different LCYs. This study confirmed the
function of the novel CsLcyB3, which will expand
the understanding of carotenoid biosynthesis in C.
sativus and provide a new candidate for the bioengineered
production of valuable carotenoids.