Characterization of Triterpene Saponin Glycyrrhizin Transport by Glycyrrhiza glabra

Abstract

Glycyrrhizin (GL), a triterpene compound produced by Glycyrrhiza species, is a crucial pharmacologically active component of crude drugs. In contrast to the biosynthesis of GL in plants, little is known about GL transport and accumulation in plants. The transport mechanism of GL was characterized using cultured cells of Glycyrrhiza glabra. Cultured cells of G. glabra efficiently incorporated exogenously supplied GL. Proton pump inhibitors, such as probenecid and niflumic acid, as well as a protonophore (carbonylcyanide m-chlorophenylhydrazone), markedly inhibited GL uptake by cultured cells, whereas vanadate exhibited a moderate inhibition. Furthermore, GL transport by G. glabra tonoplast vesicles is dependent not on a H+-electrochemical gradient but MgATP and is markedly inhibited by vanadate. These results suggest that GL uptake by cultured cells is mediated by a H+-symporter in the plasma membrane and an ATP-binding cassette transporter, which has high specificity for the aglycone structure of GL on the tonoplast.

Advances in Engineering Nucleotide Sugar Metabolism for Natural Product Glycosylation in Saccharomyces cerevisiae

“…With the synthesis of large molecules that come from heterologous species, transporters and accessory proteins may become increasingly important for the glycosylation of these natural products. The plant vacuole is often used to store secondary metabolites like saponins, and ABC-type transporters are likely used to allow these metabolites to enter the vacuole. , For example, avenacin A1 is a saponin found in Avena strigosa, where the last two biosynthetic steps occur in the vacuole, including the final glycosylation step, and this molecule could be synthesized in N. benthamiana without the addition of any transporters. , These transporters are largely uncharacterized, though it is likely that many plants share this machinery.…”

Terpenoid Transport in Plants: How Far from the Final Picture?

“…Finally, a recent study reported the identification of four members of plasma membrane-localized ABCG transporters in Salvia miltiorrhiza Bunge, a plant used in traditional Chinese medicine to treat cardiovascular and cerebrovascular diseases; these transporters could be potentially involved in the export of tanshinone (a lipophilic diterpene) and salvianolic acid (a hydrophilic phenolic compound), which are metabolites highly accumulated in the roots and rhizomes of S. miltiorrhiza [ 129 ]. Additionally, in the present Special Issue, Kato and coauthors described the transport of the triterpene saponin glycyrrhizin in Glycyrrhiza glabra (licorice plant) by a H + -symporter in the plasma membrane and by an ATP-binding cassette transporter in the vacuole (with a high specificity for the aglycone form) [ 130 ].…”