Cloning and Functional Characterization of a Lycopene ?-Cyclase from Macrophytic Red Alga Bangia fuscopurpurea.

ABSTRACT: Lycopene cyclases cyclize the open ends of acyclic lycopene (?,?-carotene) into ?- or ?-ionone rings in the crucial bifurcation step of carotenoid biosynthesis. Among all carotenoid constituents, ?-carotene (?,?-carotene) is found in all photosynthetic organisms, except for purple bacteria and heliobacteria, suggesting a ubiquitous distribution of lycopene ?-cyclase activity in these organisms. In this work, we isolated a gene (BfLCYB) encoding a lycopene ?-cyclase from Bangia fuscopurpurea, a red alga that is considered to be one of the primitive multicellular eukaryotic photosynthetic organisms and accumulates carotenoid constituents with both ?- and ?-rings, including ?-carotene, zeaxanthin, ?-carotene (?,?-carotene) and lutein. Functional complementation in Escherichia coli demonstrated that BfLCYB is able to catalyze cyclization of lycopene into monocyclic ?-carotene (?,?-carotene) and bicyclic ?-carotene, and cyclization of the open end of monocyclic ?-carotene (?,?-carotene) to produce ?-carotene. No ?-cyclization activity was identified for BfLCYB. Sequence comparison showed that BfLCYB shares conserved domains with other functionally characterized lycopene cyclases from different organisms and belongs to a group of ancient lycopene cyclases. Although B. fuscopurpurea also synthesizes ?-carotene and lutein, its enzyme-catalyzing ?-cyclization is still unknown.

SUBMITTER: Cao TJ 

PROVIDER: S-EPMC5408262 | biostudies-literature | 2017 Apr

REPOSITORIES: biostudies-literature