Abstract
Recently, we have identified pigments of Anabaena sp. PCC7120 and Nostoc punctiforme PCC73102: myxol 2'-fucoside (not rhamnoside), 4-ketomyxol 2'-fucoside, β-carotene, echinenone and canthaxanthin. In this study, we identified pigments of Anabaena variabilis ATCC29413. Myxol (5%, mol% of total carotenoids) and 4-hydroxymyxol (2%) bound no glycosides. Other carotenoids were β-carotene (51%), echinenone (22%) and canthaxanthin (20%). As genomic draft sequence of this strain is available on the Web, the pathway of carotenoid synthesis can be discussed. β-Carotene ketolase (CrtO/W) can introduce keto group to both β-carotene and echinenone to produce echinenone and canthaxanthin, respectively. β-Carotene hydroxylase (CrtR) seems to have unique characteristics, that is, β-end group of deoxymyxol is a good substrate to produce myxol, but that of β-carotene is not a substrate to produce zeaxanthin. Different characteristics of crt-genes might be caused various carotenoids in cyanobacteria. Glycosyl transferase might be inactive, since carotenoid glycosides are absent in this strain.
