Ziegler Jörg, Voigtländer Susan, Schmidt Jürgen, Kramell Robert, Miersch Otto, Ammer Christian, Gesell Andreas, Kutchan Toni M
Leibniz Institute of Plant Biochemistry, Weinberg 3, D-06120 Halle, Germany.
Plant J. 2006 Oct;48(2):177-92. doi: 10.1111/j.1365-313X.2006.02860.x. Epub 2006 Sep 13.
Plants of the order Ranunculales, especially members of the species Papaver, accumulate a large variety of benzylisoquinoline alkaloids with about 2500 structures, but only the opium poppy (Papaver somniferum) and Papaver setigerum are able to produce the analgesic and narcotic morphine and the antitussive codeine. In this study, we investigated the molecular basis for this exceptional biosynthetic capability by comparison of alkaloid profiles with gene expression profiles between 16 different Papaver species. Out of 2000 expressed sequence tags obtained from P. somniferum, 69 show increased expression in morphinan alkaloid-containing species. One of these cDNAs, exhibiting an expression pattern very similar to previously isolated cDNAs coding for enzymes in benzylisoquinoline biosynthesis, showed the highest amino acid identity to reductases in menthol biosynthesis. After overexpression, the protein encoded by this cDNA reduced the keto group of salutaridine yielding salutaridinol, an intermediate in morphine biosynthesis. The stereoisomer 7-epi-salutaridinol was not formed. Based on its similarities to a previously purified protein from P. somniferum with respect to the high substrate specificity, molecular mass and kinetic data, the recombinant protein was identified as salutaridine reductase (SalR; EC 1.1.1.248). Unlike codeinone reductase, an enzyme acting later in the pathway that catalyses the reduction of a keto group and which belongs to the family of the aldo-keto reductases, the cDNA identified in this study as SalR belongs to the family of short chain dehydrogenases/reductases and is related to reductases in monoterpene metabolism.
毛茛目植物，尤其是罂粟属的物种，能积累大约2500种结构的多种苄基异喹啉生物碱，但只有罂粟（Papaver somniferum）和刚毛罂粟（Papaver setigerum）能够产生具有止痛和麻醉作用的吗啡以及止咳的可待因。在本研究中，我们通过比较16种不同罂粟物种之间的生物碱谱和基因表达谱，研究了这种特殊生物合成能力的分子基础。从罂粟中获得的2000个表达序列标签中，有69个在含吗啡烷生物碱的物种中表达增加。其中一个cDNA，其表达模式与先前分离的编码苄基异喹啉生物合成中酶的cDNA非常相似，与薄荷醇生物合成中的还原酶具有最高的氨基酸同一性。过表达后，该cDNA编码的蛋白质还原了蒂巴因定中的酮基，生成蒂巴因定醇，这是吗啡生物合成中的一种中间体。未形成立体异构体7-表-蒂巴因定醇。基于其在高底物特异性、分子量和动力学数据方面与先前从罂粟中纯化的一种蛋白质的相似性，该重组蛋白被鉴定为蒂巴因定还原酶（SalR；EC 1.1.1.248）。与可待因酮还原酶不同，可待因酮还原酶是该途径中稍后起作用的一种酶，催化酮基的还原，属于醛酮还原酶家族，本研究中鉴定为SalR的cDNA属于短链脱氢酶/还原酶家族，与单萜代谢中的还原酶相关。
