Thalictrum tuberosum

RUEFFER, M., ZENK, M.H., Canadine synthase from Thalictrum tuberosum cell cultures catalyzes the formation of the methylenedioxy bridge in berberine synthesis. Phytochemistry, 1994, 36, 1219-1223. 

Administration of triply, 3C-labelled (5)-reticuline to a stable variant non-alkaloid producing cell culture line of Thalictrum tuberosum in cell culture demonstrated a very high incorporation of label into protoberberine alkaloids that were subsequently produced. Since this cell line does not produce reticuline, because the cell line lacks or has insufficient quantities of three methyltransferases that lead to the formation of reticuline, cell cultures that contain this cell line are appropriate for the study of biosynthetic studies., 3C NMR spectroscopy and CIMS were utilized to follow the time course of the metabolism, and demonstrated the rapid formation of scoulerine as a primary reaction product, followed by further tetrahydroprotoberberines and dehydroprotoberberines. The apparently reversible formation of dehydroscoulerine in significant amounts was interpreted as evidence for the role of this compound as an alkaloidal storage product from which scoulerine may be regenerated via enzymic reduction. Scoulerine, dehydroscoulerine, columbamine, and (S)-reticuline were detected by l3C NMR in the crude extracts, while berberine was detected by HPLC. The biosynthetic pathway of these protoberberines in this variant cell culture were summarized as follows [151] (S)-reticuline > scoulerine -> tetrahydrocolumbamine (hypothetical) -> columbamine -> dehydroscoulerine -> candadine -> berberine. 

The isoquinoline pathway s enzyme orthologs in other plants showed that genes of methyltransferase family such as (R,S)-reticuline 7-0-methyltransferase, coclaurine 4 -0-methyltransferase, (S)-norcoclaurine 6-0-methyltrasferase, columbamine 0-methyltransferase, coclaurine A-methyltransferase, putrescine A-methyltransferase responsible for the production of reticuline, coclaurine, norcoclaurine, columbaine have been reported from Papaver somniferum, Coptis japonica, Thalictrum flavum, Thalictrum tuberosum, Coffea liberica, Cojfea arabica, Cojfea canephora, Nicotiana tabacum. Solarium tuberosum. Datura stramonium, Hyoscyamus niger, and Atropa belladonna. Pathway contains information of about four alkaloids such as dopamine, colchicine, ephedrine, and methamphetamine and identified two missing links. 

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