4-Ketoantheraxanthin, a novel carotenoid produced by the combination of the bacterial enzyme β-carotene ketolase CrtW and endogenous carotenoid biosynthetic enzymes in higher plants

✍ Scribed by Kazutoshi Shindo; Tomohisa Hasunuma; Emiko Asagi; Aya Sano; Eri Hotta; Noriko Minemura; Chikahiro Miyake; Takashi Maoka; Norihiko Misawa

• Book ID: 104095233
• Publisher: Elsevier Science
• Year: 2008
• Tongue: French
• Weight: 113 KB
• Volume: 49
• Category: Article
• ISSN: 0040-4039
• DOI: 10.1016/j.tetlet.2008.03.077

✦ Synopsis

Higher plants do not ordinarily possess ketocarotenoids due to the absence of a carotenoid ketolase enzyme. We expressed genes coding for marine-bacterial enzymes b-carotene ketolase (CrtW) and b-carotene hydroxylase (CrtZ) in tobacco plants (Nicotiana tabacum) by transplastomic engineering. A novel carotenoid, 4-ketoantheraxanthin, was isolated from the leaves of the tobacco transformants. The structure of 4-ketoantheraxanthin was determined to be (3S,3 0 S,5 0 R,6 0 S)-5 0 ,6 0 -epoxy-3,3 0 -dihydroxy-b,b-caroten-4-one by analysis of the MS, NMR, and CD data. This carotenoid was considered to be synthesized by a 4-ketolation reaction by CrtW of antheraxanthin that had been synthesized by the endogenous carotenoid biosynthetic enzymes present in higher plants and CrtZ. 4-Ketoantheraxanthin was also shown to have potent antioxidative activity against a 1 O 2 suppression model.