State Key Laboratory of Bioactive Substance and Function of Natural Medicines, CAMS Key Laboratory of Enzyme and Biocatalysis of Natural Drugs, and NHC Key Laboratory of Biosynthesis of Natural Products, Institute of Materia Medica, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100050, China.
Institute of Medicinal Biotechnology, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100050, China.
J Nat Prod. 2023 Jul 28;86(7):1815-1823. doi: 10.1021/acs.jnatprod.3c00331. Epub 2023 Jun 19.
Triterpenoids are a large and medicinally important group of natural products with a wide range of biological and pharmacological effects. Among them, malabaricane-type triterpenoids are a rare group of terpenoids with a 6,6,5-tricyclic ring system, and a few malabaricane triterpene synthases have been characterized to date. Here, an arabidiol synthase AmAS for the formation of the malabaricane-type 6,6,5-tricyclic triterpenoid skeleton in astramalabaricosides biosynthesis was characterized from . Multiple sequence alignment, site-directed mutagenesis, and molecular docking of AmAS reveal that residues Q256 and Y258 are essential for AmAS activity, and the triad motif IIH725-727 was the critical residue necessary for its product specificity. Mutation of IIH725-727 with VFN led to the formation of seven tricyclic, tetracyclic, and pentacyclic triterpenoids (-). Glycosylation of malabaricane-type triterpenoids in the biosynthesis of astramalabaricosides was also explored. Three triterpenoids (, , and ) displayed potent inhibitory effects against influenza A virus in vitro. These findings provide insights into malabaricane-type triterpenoids biosynthesis in and access to diverse bioactive triterpenoids for drug discovery.
三萜类化合物是一大类具有广泛生物和药理作用的重要天然产物，其中马拉巴烷型三萜类化合物是一类具有 6,6,5-三环体系的罕见萜类化合物，迄今为止已有少数马拉巴烷型三萜类化合物合成酶得到了表征。在这里，我们从 中鉴定了一个用于形成马拉巴烷型 6,6,5-三环三萜骨架的阿拉伯醇合酶 AmAS，该酶参与 astramalabaricosides 生物合成。AmAS 的多重序列比对、定点突变和分子对接揭示了残基 Q256 和 Y258 对 AmAS 活性至关重要，三联基序 IIH725-727 是其产物特异性所必需的关键残基。将 IIH725-727 突变为 VFN 导致形成了七种三环、四环和五环三萜 (-)。我们还探索了 astramalabaricosides 生物合成中马拉巴烷型三萜类化合物的糖基化。三种三萜类化合物（、和 ）在体外显示出对甲型流感病毒的强烈抑制作用。这些发现为 中马拉巴烷型三萜类化合物的生物合成提供了深入了解，并为药物发现提供了多种具有生物活性的三萜类化合物。
