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S. Takaichi
2.3 Carotenogenesis Pathways, Enzymes, and Genes
Carotenogenesis pathways and enzymes among oxygenic phototrophs have been
mainly investigated in cyanobacteria (Takaichi and Mochimaru 2007) and land plants
(Britton 1998). Especially in land plants, carotenogenesis pathways and characteristics of enzymes are studied in detail (Fig. 2.2). However, algae contain common
pathways to land plants and also additional algae-specific pathways, which have been
proposed solely based on the chemical structures of carotenoids (Fig. 2.2) (Takaichi
2011). Some common carotenogenic genes in algae are suggested from homology
with other known genes (Frommolt et al. 2008; Bertrand 2010), but most of the genes
and enzymes involved in the algae-specific pathways remain unknown (Fig. 2.2). In
cyanobacteria, since carotenoid compositions are different from those in land plants
and algae, the pathways and enzymes are also different from those in Fig. 2.2, and are
shown instead in Fig. 2.3. In addition, the carotenogenic enzymes and genes, whose
Fig. 2.2 Carotenogenesis pathways and enzymes, whose functions are confirmed, in oxygenic
phototrophs