Abstract
Glycyrrhizin is the major triterpene saponin produced by Glycyrrhiza glabra, and stored in the roots and stolons. We examined a transport mechanism of glycyrrhizin by using cultured G. glabra cells, because they cannot synthesize glycyrrhizin de novo. We showed that the G. glabra cells were able to uptake glycyrrhizin from the medium. Treatment with several inhibitors suggested that glycyrrhizin uptake depended on ATP level. Anion blockers, pH gradient destroyers, and glycyrrhetinic acid inhibited glycyrrhizin uptake. To clarify the molecular mechanism of glycyrrhizin transport, membrane vesicles of the G. glabra cells were fractionated using a discontinuous sucrose gradient. The tonoplast-enriched vesicles exhibited ATP-dependent glycyrrhizin uptake activity. Further characterization of glycyrrhizin transport using various inhibitors revealed that sodium orthovanadate, a P-type ATPase inhibitor, and glycyrrhetinic acid strongly inhibited glycyrrhizin transport.
