Functional characterization of a novel benzylisoquinolineO-methyltransferase suggests its involvement in papaverine biosynthesis in opium poppy (Papaver somniferumL)

摘要: Summary The benzylisoquinoline alkaloids are a highly diverse group of about 2500 compounds which accumulate in species-specific manner. Despite the numerous could be identified, biosynthetic pathways and participating enzymes or cDNAs characterized only for few selected members, whereas biosynthesis majority is still largely unknown. In an attempt to characterize additional steps at molecular level, integration alkaloid transcript profiling across Papaver species was performed. This analysis showed high expression expressed sequence tag (EST) unknown function somniferum varieties. After full-length cloning open reading frame analysis, this EST classified as member class II type O-methyltransferase protein family. It related O-methyltransferases from biosynthesis, amino acid 68% identical residues norcoclaurine 6-O-methyltransferase. However, rather than methylating norcoclaurine, recombinant methylated norreticuline position seven with Km 44 μm using S-adenosyl-l-methionine cofactor. Of all substrates tested, converted. Even minor changes backbone were not tolerated by enzyme. Accordingly, enzyme named 7–O-methyltransferase (N7OMT). represents novel metabolism. Expression slightly increased N7OMT P. somniferum varieties containing papaverine, suggesting its involvement partially pharmaceutically important compound.