Carotenogenesis in cyanobacteria: CruA/CruP-type and CrtL-type lycopene cyclases
Kenjiro Sugiyama, Shinichi Takaichi
Abstract
synthetic bacteria, and to have given rise to plant chloroplasts through evolution and symbiosis. The carotenoid structures and carotenogenesis pathways differ among photosynthetic bacteria, cyanobacteria, and chloroplasts, and, accordingly, carotenoids seem to change continuously. It is interesting to speculate on how these different carotenogenesis pathways have evolved and been obtained. Cyanobacteria can synthesize a variety of carotenoids. Most ordinary cyanobacteria contain -carotene and its derivatives such as zeaxanthin, echinenone, and nostoxanthin; and also unique carotenoid glycosides, such as myxol fucoside and ketomyxol chinovoside These carotenoids are cyclized at one or both ends of the structure. This cyclization reaction is catalyzed by lycopene cyclase. Thus far, several types of lycopene cyclases have been confirmed in various organisms including cyanobacteria Furthermore, this is the branching point of -carotene and -carotene: from -carotene, echinenone, zeaxanthin and nostoxanthin are produced; and from -carotene, myxol glycoside, ketomyxol glycoside and 2-hycroxymyxol glycoside are produced In this review, we summarize the carotenogenesis pathway, the functional enzymes as well as genes in cyanobacteria. We particularly focus on the cyclization of lycopene by distinct types of lycopene cyclases.