SummaryAlthough natural insecticides pyrethrins produced by Tanacetum cinerariifolium are used worldwide to control insect pest species, little information is known of their biosynthesis. From the buds of T. cinerariifolium, we have purified a protein that is able to transfer the chrysanthemoyl group from the coenzyme A (CoA) thioester to pyrethrolone to produce pyrethrin I and have isolated cDNAs that encode the enzyme. To our surprise, the active principle was not a member of a known acyltransferase family but a member of the GDSL lipase family. The recombinant enzyme (TcGLIP) was expressed in Escherichia coli and displayed the acyltransferase reaction with high substrate specificity, recognized the absolute configurations of three asymmetric carbons and also showed esterase activity. A S40A mutation in the Block I domain reduced both acyltransferase and esterase activities, which suggested an important role of this serine residue in these two activities. The signal peptide directed the localization of TcGLIP::enhanced green fluorescent protein (EGFP) fusion, as well as EGFP, to the extracellular space. High TcGLIP gene expression was observed in the leaves of mature plants and seedlings as well as in buds and flowers, a finding that was consistent with the pyrethrin I content in these parts. Expression was enhanced in response to wounding, which suggested that the enzyme plays a key role in the defense mechanism of T. cinerariifolium.
摘要尽管由Tanacetum cinerariifolium生产的天然杀虫剂除虫菊酯在全球范围内被用于控制害虫种类,但有关其生物合成的信息却知之甚少。我们从 T. cinerariifolium 的芽中纯化出了一种蛋白质,这种蛋白质能够将菊酰基从辅酶 A(CoA)硫酯转移到除虫菊酯中,从而产生除虫菊酯 I,我们还分离出了编码这种酶的 cDNA。令我们惊讶的是,这种酶的活性原理并不是已知的酰基转移酶家族的成员,而是 GDSL 脂肪酶家族的成员。重组酶(TcGLIP)在大肠杆菌中表达,显示出具有高度底物特异性的酰基转移酶反应,能识别三个不对称碳的绝对构型,还显示出酯酶活性。Block I 结构域中的 S40A 突变降低了酰基转移酶和酯酶的活性,这表明该丝氨酸残基在这两种活性中起着重要作用。信号肽引导 TcGLIP::enhanced 绿色荧光蛋白(EGFP)融合体以及 EGFP 定位于细胞外空间。在成熟植株和幼苗的叶片以及芽和花中观察到 TcGLIP 基因的高表达,这一发现与这些部位的除虫菊酯 I 含量一致。该酶在 T. cinerariifolium 的防御机制中起着关键作用。