Isolation and characterization of a carotenoid oxygenase gene from Chlorella zofingiensis (Chlorophyta)
Isolation and characterization of a carotenoid oxygenase gene from Chlorella zofingiensis (Chlorophyta)
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DOI：
10.1007/s00253-005-0166-8
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发表时间：
2006-07-01
影响因子：
5
通讯作者：
Chen, Feng
中科院分区：
文献类型：
--
作者：
Huang, Jun-Chao;Wang, Yan;Chen, Feng
绿藻小球藻（Chlorella zoofingiensis）在黑暗异养生长条件下产生大量有价值的类酮胡萝卜素虾青素，这使得它有可能用于虾青素的商业生产，作为饲料添加剂、着色剂和保健品。在这里，我们报道了一个β -胡萝卜素加氧酶（CRTO）基因的鉴定和表征，该基因直接参与了zofingiensis中类酮胡萝卜素的生物合成。crtO基因的开放阅读框被三个分别为243,318和351bp的内含子打断，编码一个由312个氨基酸残基组成的多肽。zofingiensis基因组中仅检测到1个crtO基因。此外，在葡萄糖处理下，crtO基因的表达会短暂上调。在大肠杆菌中的功能互补表明，crtO基因的编码蛋白不仅能通过紫棘烯酮将β -胡萝卜素转化为角黄素，而且能通过阿多黄质将玉米黄质转化为虾青素，具有正常的crtO活性。基于双功能的CRTO，我们预测了zofingiensis虾青素的生物合成途径，并将其命名为类胡萝卜素4,4′- β -离子环加氧酶。
The green alga Chlorella zofingiensis produces large amounts of the valuable ketocarotenoid astaxanthin under dark, heterotrophic growth conditions, making it potentially employable for commercial production of astaxanthin as feed additives, colorants, and health products. Here, we report the identification and characterization of a beta-carotene oxygenase (CRTO) gene that is directly involved in the biosynthesis of ketocarotenoids in C. zofingiensis. The open reading frame of the crtO gene, which is interrupted by three introns of 243, 318, and 351 bp, respectively, encodes a polypeptide of 312 amino acid residues. Only one crtO gene was detected in the genome of C. zofingiensis. Furthermore, the expression of the crtO gene was transiently up-regulated upon glucose treatment. Functional complementation in Escherichia coli showed that the coding protein of the crtO gene not only exhibits normal CRTO activity by converting beta-carotene to canthaxanthin via echinenone, but also displays a high enzymatic activity of converting zeaxanthin to astaxanthin via adonixanthin. Based on the bifunctional CRTO, a predicted pathway for astaxanthin biosynthesis in C. zofingiensis is described, and the CRTO is termed as carotenoid 4,4'-beta-ionone ring oxygenase.