INDUCTION OF A SPECIFIC METHYLTRANSFERASE ACTIVITY REGULATING BERBERINE BIOSYNTHESIS BY CYTOKININ IN THALICTRUM-MINUS CELL-CULTURES

The effects of cytokinins on the activities of seven enzymes involved in the early steps and one in the last step of berberine biosynthesis in Thalictrum minus var. hypoleucum cell cultures were examined. Of these enzymes, norcoclaurine-O-methyltransferase (NCMT) was found to be markedly activated especially by 6-benzylaminopurine (BAP), reaching the highest level (34.2 pkat mg(-1) protein) six days after administration of the cytokinin. Furthermore, berberine production increased in proportion to the NCMT activity or to the BAP concentration. These results suggest that the induction of berberine production by cytokinin in T. minus cell cultures is primarily attributable to a remarkable increase in the activity of a specific methyltransferase that catalyses the first methylation of norcocluarine to yield coclaurine, a principal intermediate in the biosynthesis of protoberberine alkaloids.