Molecular Cloning and Characterization of a Xanthone Prenyltransferase from Hypericum calycinum Cell Cultures
作者:Tobias Fiesel、Mariam Gaid、Andreas Müller、Joana Bartels、Islam El-Awaad、Till Beuerle、Ludger Ernst、Sönke Behrends、Ludger Beerhues
DOI:10.3390/molecules200915616
日期:——
In plants, prenylation of metabolites is widely distributed to generate compounds with efficient defense potential and distinct pharmacological activities profitable to human health. Prenylated compounds are formed by members of the prenyltransferase (PT) superfamily, which catalyze the addition of prenyl moieties to a variety of acceptor molecules. Cell cultures of Hypericum calycinum respond to elicitor treatment with the accumulation of the prenylated xanthone hyperxanthone E. A cDNA encoding a membrane-bound PT (HcPT) was isolated from a subtracted cDNA library and transcript preparations of H. calycinum. An increase in the HcPT transcript level preceded hyperxanthone E accumulation in cell cultures of H. calycinum treated with elicitor. The HcPT cDNA was functionally characterized by expression in baculovirus-infected insect cells. The recombinant enzyme catalyzed biosynthesis of 1,3,6,7-tetrahydroxy-8-prenylxanthone through regiospecific C–8 prenylation of 1,3,6,7-tetrahydroxyxanthone, indicating its involvement in hyperxanthone E formation. The enzymatic product shared significant structural features with the previously reported cholinesterase inhibitor γ-mangostin. Thus, our findings may offer a chance for semisynthesis of new active agents to be involved in the treatment of Alzheimer’s disease.
在植物中,代谢物的预炔化作用分布广泛,可产生具有高效防御潜力和独特药理活性的化合物,从而有益于人类健康。前炔基化化合物是由前炔基转移酶(PT)超家族成员形成的,它们能催化将前炔基分子添加到各种受体分子中。从 H. calycinum 的 cDNA 文库和转录本制备物中分离出了编码膜结合 PT(HcPT)的 cDNA。HcPT 转录本水平的增加先于 H. calycinum 细胞培养物中超黄酮 E 的积累。通过在杆状病毒感染的昆虫细胞中表达 HcPT cDNA,确定了其功能特征。重组酶通过1,3,6,7-四羟基氧杂蒽酮的特异性C-8前炔基化催化1,3,6,7-四羟基-8-异戊烯基氧杂蒽酮的生物合成,表明其参与了超氧杂蒽酮E的形成。 该酶产物与之前报道的胆碱酯酶抑制剂γ-曼戈斯汀具有显著的结构特征。因此,我们的发现可能为半合成新的活性剂提供了机会,从而参与阿尔茨海默病的治疗。