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Complete Biosynthetic Pathway of the C₅₀ Carotenoid Bacterioruberin from Lycopene in the Extremely Halophilic Archaeon Haloarcula japonica

Yang, Ying, Yatsunami, Rie, Ando, Ai, Miyoko, Nobuhiro, Fukui, Toshiaki, Takaichi, Shinichi, Nakamura, Satoshi
Journal of bacteriology 2015 v.197 no.9 pp. 1614-1623
Haloarcula, biochemical pathways, enzymes, genes, lycopene, mutants, sodium chloride
Haloarcula japonica , an extremely halophilic archaeon that requires high concentrations of NaCl for growth, accumulates the C ₅₀ carotenoid bacterioruberin (BR). By homology analysis, a gene cluster, including c0507 , c0506 , and c0505 , was found and predicted to be involved in the synthesis of bacterioruberin. To elucidate the function of the encoded enzymes, we constructed Ha. japonica mutants of these genes and analyzed carotenoids produced by the mutants. Our research showed that c0507 , c0506 , and c0505 encoded a carotenoid 3,4-desaturase (CrtD), a bifunctional lycopene elongase and 1,2-hydratase (LyeJ), and a C ₅₀ carotenoid 2″,3″-hydratase (CruF), respectively. The above three carotenoid biosynthetic enzymes catalyze the reactions that convert lycopene to bacterioruberin in Ha. japonica . This is the first identification of functional CrtD and CruF in archaea and elucidation of the complete biosynthetic pathway of bacterioruberin from lycopene. IMPORTANCE Haloarcula japonica , an extremely halophilic archaeon, accumulates the C ₅₀ carotenoid bacterioruberin (BR). In this study, we have identified three BR biosynthetic enzymes and have elucidated their functions. Among them, two enzymes were found in an archaeon for the first time. Our results revealed the biosynthetic pathway responsible for production of BR in Ha. japonica and provide a basis for investigating carotenoid biosynthetic pathways in other extremely halophilic archaea. Elucidation of the carotenoid biosynthetic pathway in Ha. japonica may also prove useful for producing the C ₅₀ carotenoid BR efficiently by employing genetically modified haloarchaeal strains.