Abstract
Carotenoids in cyanobacteria have diversity from species to species. Last year, we presented the identification of pigments in Anabaena sp. PCC7120; myxol-fucoside, ketomyxol-fucoside, β-carotene, echinenone, and canthaxanthin. In Anabaenas, there are no zeaxanthin, one of major pigments in Synechocystis sp. PCC6803.
In this study, we propose a biosynthetic pathway in A. 7120. Nine genes have already been functionally identified in other bacteria, and close homologues of these genes were found in the genome of A. 7120 by similarity search. We found two homologues of β-carotene ketolase; one is alr3189, a homologue of crtW in Nostoc punctiforme PCC73102 and the other one is all3744, a homologue of crtO in S. 6803. An all3744-deletion mutant lacked echinenone and canthaxanthin, but contained ketomyxol- fucoside. This result indicates that ketolation of β-carotene and myxol-fucoside are catalyzed at least two different ketolases. We are also trying to disrupt other carotenogenesis genes.
