Marine Biological Manufacturing Center of Fuzhou Institute of Oceanography, Fuzhou University, Fuzhou 350108, China.
Technical Innovation Service Platform for High-Value and High-Quality Utilization of Marine Organism, Fuzhou University, Fuzhou 350108, China.
Mar Drugs. 2023 Jul 23;21(7):418. doi: 10.3390/md21070418.
Lutein is a high-value carotenoid with many human health benefits. Lycopene β- and ε-cyclases (LCYB and LCYE, respectively) catalyze the cyclization of lycopene into distinct downstream branches, one of which is the lutein biosynthesis pathway, via α-carotene. Hence, LCYB and LCYE are key enzymes in lutein biosynthesis. In this study, the coding genes of two lycopene cyclases (CsLCYB and CsLCYE) of a lutein-enriched marine green microalga, FZU60, were isolated and identified. A sequence analysis and computational modeling of CsLCYB and CsLCYE were performed using bioinformatics to identify the key structural domains. Further, a phylogenetic analysis revealed that CsLCYB and CsLCYE were homogeneous to the proteins of other green microalgae. Subcellular localization tests in showed that CsLCYB and CsLCYE localized in chloroplasts. A pigment complementation assay in revealed that CsLCYB could efficiently β-cyclize both ends of lycopene to produce β-carotene. On the other hand, CsLCYE possessed a strong ε-monocyclase activity for the production of δ-carotene and a weak ε-bicyclic activity for the production of ε-carotene. In addition, CsLCYE was able to catalyze lycopene into β-monocyclic γ-carotene and ultimately produced α-carotene with a β-ring and an ε-ring via γ-carotene or δ-carotene. Moreover, the co-expression of CsLCYB and CsLCYE in revealed that α-carotene was a major product, which might lead to the production of a high level of lutein in FZU60. The findings provide a theoretical foundation for performing metabolic engineering to improve lutein biosynthesis and accumulation in FZU60.
叶黄素是一种具有高附加值的类胡萝卜素，对人体健康有诸多益处。番茄红素 β-和 ε-环化酶（LCYB 和 LCYE，分别）通过 α-胡萝卜素催化番茄红素环化为不同的下游分支，其中之一是叶黄素生物合成途径，因此，LCYB 和 LCYE 是叶黄素生物合成的关键酶。本研究从富含叶黄素的海洋绿藻 FZU60 中分离并鉴定了两种番茄红素环化酶（CsLCYB 和 CsLCYE）的编码基因。使用生物信息学对 CsLCYB 和 CsLCYE 进行序列分析和计算建模，以鉴定关键结构域。进一步的系统发育分析表明，CsLCYB 和 CsLCYE 与其他绿藻的蛋白质具有同源性。在 中进行的亚细胞定位测试表明，CsLCYB 和 CsLCYE 定位于叶绿体中。在 中进行的色素互补测定表明，CsLCYB 能够有效地 β-环化番茄红素的两端，生成 β-胡萝卜素。另一方面，CsLCYE 具有很强的 ε-单环化酶活性，可生成 δ-胡萝卜素，弱的 ε-双环化酶活性，可生成 ε-胡萝卜素。此外，CsLCYE 能够将番茄红素催化为 β-单环 γ-胡萝卜素，并最终通过 γ-胡萝卜素或 δ-胡萝卜素生成具有 β-环和 ε-环的 α-胡萝卜素。此外，在 中共同表达 CsLCYB 和 CsLCYE 表明，α-胡萝卜素是主要产物，这可能导致 FZU60 中叶黄素的高水平产生。这些发现为进行代谢工程以提高 FZU60 中叶黄素的生物合成和积累提供了理论基础。
