Functional Identification of Two Types of Carotene Hydroxylases from the Green Alga Dunaliella bardawil Rich in Lutein.,ACS Synthetic Biology

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Functional Identification of Two Types of Carotene Hydroxylases from the Green Alga Dunaliella bardawil Rich in Lutein.
ACS Synthetic Biology ( IF 3.7 ) Pub Date : 2020-05-14 , DOI: 10.1021/acssynbio.0c00070
Ming-Hua Liang ₁ , Hong Xie ₁ , Hao-Hong Chen ₁ , Zhi-Cong Liang ₁ , Jian-Guo Jiang ₁

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The salt-tolerant unicellular alga Dunaliella bardawil FACHB-847 can accumulate large amounts of lutein, but the underlying cause of massive accumulation of lutein is still unknown. In this study, genes encoding two types of carotene hydroxylases, i.e., β-carotene hydroxylase (DbBCH) and cytochrome P450 carotenoid hydroxylase (DbCYP97s; DbCYP97A, DbCYP97B, and DbCYP97C), were cloned from D. bardawil. Their substrate specificities and enzyme activities were tested through functional complementation assays in Escherichia coli. It was showed that DbBCH could catalyze the hydroxylation of the β-rings of both β- and α-carotene, and displayed a low level of ε-hydroxylase. Unlike CYP97A from higher plants, DbCYP97A could not hydroxylate β-carotene. DbCYP97A and DbCYP97C showed high hydroxylase activity toward the β-ring and ε-ring of α-carotene, respectively. DbCYP97B displayed minor activity toward the β-ring of α-carotene. The high accumulation of lutein in D. bardawil may be due to the multiple pathways for lutein biosynthesis generated from α-carotene with zeinoxanthin or α-cryptoxanthin as intermediates by DbBCH and DbCYP97s. Taken together, this study provides insights for understanding the underlying reason for high production of lutein in the halophilic green alga D. bardawil FACHB-847.

中文翻译：

叶绿素中富含绿藻类杜氏杜鹃的两种类型的胡萝卜素羟化酶的功能鉴定。

耐盐的单细胞藻杜氏杜氏藻FACHB-847可以积累大量的叶黄素，但是叶黄素大量积累的根本原因仍然未知。在这项研究中，从D. bardawil克隆了编码两种类型的胡萝卜素羟化酶的基因，即β-胡萝卜素羟化酶（DbBCH）和细胞色素P450类胡萝卜素羟化酶（DbCYP97s； DbCYP97A，DbCYP97B和DbCYP97C）。它们的底物特异性和酶活性通过大肠杆菌中的功能互补分析进行了测试。结果表明，DbBCH可以催化β-和α-胡萝卜素的β-环的羟基化，并显示出低水平的ε-羟化酶。与高等植物中的CYP97A不同，DbCYP97A不能羟化β-胡萝卜素。DbCYP97A和DbCYP97C分别对α-胡萝卜素的β-环和ε-环显示高羟化酶活性。DbCYP97B对α-胡萝卜素的β环显示较小的活性。叶黄素在D. Bardawil中的高积累可能是由于以玉米黄素或α-隐黄质为中间体的α-胡萝卜素通过DbBCH和DbCYP97s产生的多种叶黄素生物合成途径。两者合计，这项研究提供了见解，以了解在嗜盐绿藻D. bardawil FACHB-847中叶黄素高产量的根本原因。

更新日期：2020-06-19

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