Camellia sasanqua is an important economic plant that is rich in lipophilic triterpenols with pharmacological activities including antiallergic, anti-inflammatory, and anticancer activities. However, the key enzymes related to triterpene biosynthesis have seldom been studied in C. sasanqua. Oxidosqualene cyclases (OSCs) are the rate-limiting enzymes related to triterpene biosynthesis. In this study, seven putative OSC genes (CsOSC1-7) were mined from the C. sasanqua transcriptome. Six CsOSCs were characterized for the biosynthesis of diverse triterpene skeletons, including α-amyrin, β-amyrin, δ-amyrin, dammarenediol-II, ψ-taraxasterol, taraxasterol, and cycloartenol by the heterologous expression system. CsOSC3 was a multiple functional α-amyrin synthase. Three key residues, Trp260, Tyr262, and Phe415, are critical to the catalytic performance of CsOSC3 judging from the results of molecular docking and site-directed mutagenesis. These findings provide important insights into the biosynthesis pathway of triterpenes in C. sasanqua.

中文翻译：

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山茶花多种三萜生物合成中的氧化角鲨烯环化酶

茶花是一种重要的经济植物，富含亲脂性三萜类化合物，具有抗过敏、抗炎、抗癌等药理活性。然而，山茶花中与三萜生物合成相关的关键酶却鲜有研究。氧化角鲨烯环化酶（OSCs）是与三萜生物合成相关的限速酶。在这项研究中，七个推定的OSC基因 ( CsOSC1-7 ) 从山茶中被挖掘出来。转录组。通过异源表达系统对六种 CsOSC 进行了表征，用于生物合成不同的三萜骨架，包括 α-香脂素、β-香脂素、δ-香脂素、达马烯二醇-II、ψ-蒲公英甾醇、蒲草甾醇和环阿霉素。CsOSC3 是一种多功能 α-香树脂醇合酶。从分子对接和定点诱变的结果来看，三个关键残基 Trp260、Tyr262 和 Phe415 对 CsOSC3 的催化性能至关重要。这些发现为山茶花中三萜的生物合成途径提供了重要的见解。