Plants of the order Ranunculales, especially members of the species Papaver, accumulate a large variety of benzylisoquinoline alkaloids with about 2,500 structures. But only the opium poppy, Papaver somniferum, and Papaver setigerum, are able to produce morphinan alkaloids such as the analgesic morphine or the antitussive codeine. We investigated the molecular basis for this exceptional biosynthetic capability by comparison of alkaloid profiles with gene expression profiles between sixteen different Papaver species and identified one cDNA which exhibits very similar expression pattern to previously isolated cDNAs coding for enzymes in benzylisoquinoline biosynthesis and which showed the highest amino acid identity to reductases in menthol biosynthesis. When expressed, the protein encoded by this cDNA reduced the keto group of salutaridine yielding salutaridinol, an intermediate in morphine biosynthesis. The stereoisomer epi-salutaridinol was not formed. The encoded protein was identified as salutaridine reductase (SalR; EC 1.1.1.248) and it was found to belongs to the family of the short chain dehydrogenases / reductases.
毛茛目植物,尤其是罂粟属物种,积累了大量的苯基
异喹啉生物碱,约有2500种结构。但只有鸦片罂粟(Papaver somniferum)和刺毛罂粟(Papaver setigerum)等品种能够产生
吗啡等
镇痛药物
吗啡类
生物碱或
镇咳药可待因。我们通过比较16种不同罂粟属植物的
生物碱谱与
基因表达谱,鉴定出一个cDNA,其表达模式与之前分离的编码苯基
异喹啉生物合成酶的cDNA非常相似,并且与薄荷醇
生物合成中的还原酶具有最高的
氨基酸同源性。当表达时,这个cDNA编码的蛋白质将沙洛特啶的酮基还原为沙洛特啉醇,这是
吗啡生物合成中的中间体。而对映异构体外沙洛特啉醇并未形成。这个编码的蛋白质被鉴定为沙洛特啶还原酶(SalR;
EC 1.1.1.248),并且发现它属于短链脱氢酶/还原酶家族。