Abstract
We have identified all the carotenoids in Anabaena sp. PCC 7120: myxol fucoside, ketomyxol fucoside, β-carotene, echinenone and canthaxanthin (Takaichi et al. (2005) PCP 46, 497). Further, we have functionally determined two distinct β-carotene ketolases: CrtO (all3477) for echinenone and CrtW (alr3189) for ketomyxol synthesis (Mochimaru et al. (2005) FEBS Lett. 579, 6111).
In this study, we searched cartenogenesis enzymes by sequence homology. The enzymes, whose functions have already been confirmed in other bacteria, were chosen for the query sequences. Since a disrupted mutant of alr4009, produced (keto)-deoxymyxol fucoside instead of (keto)-myxol fucoside, its function was confirmed to be β-carotene hydrogenase (CrtR). Although the functions of CrtD and CruA were OH-γ-carotene 3,4-desaturase and lycopene cyclase, the disrupted mutants of all5123 and alr0920 had no effects on carotenoids, respectively. Therefore, these enzymes were not for carotenogenesis in Anabaena 7120. There are some differences among species, and further studies are needed.
