G chlorophyll.Fig. 3. A schematic of the putative carotenoid biosynthesis pathway in Acaryochloris. The reaction catalyzed by CrtR passes through the intermediate -cryptoxanthin.which likely provided the origin for CAO, and other poorly understood enzymes, such as the phylogenetically aberrant divinyl chlorophyllide reductase (33), which shows an unusual phylogenetic topology in A. marina (AM1 239