Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario, N1G 2W1, Canada.
NMR Center, University of Guelph, Guelph, Ontario, N1G 2W1, Canada.
Phytochemistry. 2019 Aug;164:162-171. doi: 10.1016/j.phytochem.2019.05.009. Epub 2019 May 28.
In addition to the psychoactive constituents that are typically associated with Cannabis sativa L., there exist numerous other specialized metabolites in this plant that are believed to contribute to its medicinal versatility. This study focused on two such compounds, known as cannflavin A and cannflavin B. These prenylated flavonoids specifically accumulate in C. sativa and are known to exhibit potent anti-inflammatory activity in various animal cell models. However, almost nothing is known about their biosynthesis. Using a combination of phylogenomic and biochemical approaches, an aromatic prenyltransferase from C. sativa (CsPT3) was identified that catalyzes the regiospecific addition of either geranyl diphosphate (GPP) or dimethylallyl diphosphate (DMAPP) to the methylated flavone, chrysoeriol, to produce cannflavins A and B, respectively. Further evidence is presented for an O-methyltransferase (CsOMT21) encoded within the C. sativa genome that specifically converts the widespread plant flavone known as luteolin to chrysoeriol, both of which accumulate in C. sativa. These results therefore imply the following reaction sequence for cannflavins A and B biosynthesis: luteolin ► chrysoeriol ► cannflavin A and cannflavin B. Taken together, the identification of these two unique enzymes represent a branch point from the general flavonoid pathway in C. sativa and offer a tractable route towards metabolic engineering strategies that are designed to produce these two medicinally relevant Cannabis compounds.
除了通常与大麻属植物相关的精神活性成分外，这种植物还存在许多其他专门的代谢物，据信这些代谢物有助于其药用多功能性。本研究集中于两种此类化合物，即大麻素 A 和大麻素 B。这些被prenyl 化的类黄酮专门在 C. sativa 中积累，已知在各种动物细胞模型中表现出强大的抗炎活性。然而，几乎不知道它们的生物合成。本研究采用系统发育基因组学和生物化学方法相结合，从大麻属植物中鉴定出一种芳香 prenyltransferase（CsPT3），该酶能特异性地将香叶基二磷酸（GPP）或二甲基烯丙基二磷酸（DMAPP）分别添加到甲基化黄酮 Chrysoeriol 上，分别生成大麻素 A 和大麻素 B。进一步的证据表明，C. sativa 基因组内编码的 O-甲基转移酶（CsOMT21）能够特异性地将广泛存在于植物中的黄酮类化合物木樨草素转化为 Chrysoeriol，这两种物质都在 C. sativa 中积累。因此，这些结果表明大麻素 A 和 B 的生物合成的反应序列如下：木樨草素→Chrysoeriol→大麻素 A 和大麻素 B。综上所述，这两种独特酶的鉴定代表了 C. sativa 中一般类黄酮途径的一个分支点，并为设计生产这两种具有药用相关性的大麻化合物的代谢工程策略提供了可行的途径。
