KINETICS OF ALKALOID UPTAKE BY CULTURED-CELLS OF COPTIS-JAPONICA

Cultured cells of Coptis japonica (Ranunculaceae) were shown to take up exogenously added, quaternary benzylisoquinoline alkaloids of the protoberberine type indigenous to the species in a kinetic pattern similar to an enzymatic reaction after the Michaelis-Menten equation. Isolation of protoplasts and vacuoles from the cells demonstrated that these alkaloids were exclusively transported to vacuoles to be accumulated. By contrast, magnoflorine, a quaternary benzylisoquinoline alkaloid, was barely absorbed by the cells. Furthermore, only part of magnoflorine as well as of papaverine taken up by the cells was detectable in the vacuoles, while the rest remained in the cytosol. These results suggested a high selectivity of Coptis cells in the absorption and transport of alkaloids.