Abstract
Carotenoids in cyanobacteria have diversity from species to species. Genera Anabaena and Nostoc have unique polar ketocarotenoids, ketomyxol glycosides. In Anabaena 7120, ketomyxol fucoside is obserbed (Takaichi et al., 2005, PCP). Ketolase, CrtW, is the only enzyme that functionally identified among the synthetic pathway from lycopene to ketomyxol glycosides (Mochimaru et al., 2005, FEBS Lett.). We also identified β-carotene hydroxylase, CrtR, in Anabaena 7120.
In this study, we tried to determine fucose synthase by gene disruption. From the disrupted mutant of all4826 (homologue of GDP-fucose synthase from Synechocystis 6803), more polar carotenoid glycosides than those of wild type were obtained. NMR data indicated that the glycoside moiety seemed to be different methylpentose than that of any reported myxol glycosides, such as α-L-fucose, α-L-rhamnose, and α-L-chinovose. It suggests that in Δall4826, fucose is not synthesized and the methylpentose binds to myxol as a substitute.
