Myxol 2'-dimethyl-fucoside, (3R,2'S)-myxol 2'-(2,4-di-O-methyl-alph-L-fucoside), in Synechocystis sp. PCC 6803 and nomenclature of myxoxanthophyll

Abstract

We identified the molecular structures of the carotenoids in Synechocystis sp. PCC 6803 based on absorption spectra, retention times on HPLC, FD-MS, CD, 1H- and 13C-NMR spectral data. Myxoxanthophyll in this cyanobacterium was myxol 2'-dimethyl-fucoside, (3R,2'S)-myxol 2'-(2,4-di-O-methyl-a-L-fucoside). The sugar moiety of the pigment was not rhamnose but dimethylated fucose, which has not been reported in carotenoid glycosides. The other carotenoids were ß-carotene, (3R,3'R)- zeaxanthin, echinenone, (3'R)-3'-hydroxyechinenone and deoxymyxol 2'-dimethyl- fucoside, (2'S)-deoxymyxol 2'-(2,4-di-O-methyl-a-L-fucoside). Pathway and enzymes of carotenogenesis will be discussed. Generally, the group of polar carotenoids in cyanobacteria is referred to as myxoxanthophyll, and the structure is considered to be myxol 2'-rhamnoside. Since the name myxoxanthophyll can not specify the sugar moiety and the identification of the sugar moiety is unfeasible in many cyanobacteria, we propose the following naming convention: when the sugar moiety has not been identified, the name is myxol glycoside. If the sugar moieties have been identified, the names should be, for example, myxol 2'-rhamnoside, myxol 2'-a-L-fucoside and (3R,2'S)-myxol 2'-(2,4-di-O-methyl-a-L-fucoside). The use of myxoxanthophyll should be avoided. S. Takaichi et al. (2001) Plant Cell Physiol., in press.