INTRACELLULAR-LOCALIZATION OF UDPG - P-HYDROXYBENZOATE GLUCOSYLTRANSFERASE AND ITS REACTION-PRODUCT IN LITHOSPERMUM CELL-CULTURES

Intracellular localization of p-O-beta-D-glucosylbenzoic acid (PHBOG) and its aglycone, p-hydroxybenzoic acid (PHB), a key intermediate of shikonin biosynthesis, was investigated in Lithospermum erythrorhizon cell cultures. The glucoside, which is characteristically accumulated in shikonin-free Lithospermum cell cultures, proved to be localized mainly in the vacuoles of cells. p-Hydroxybenzoate glucosyltransferase, however, was not detected in the vacuoles but exclusively in the cytosol of cells. Furthermore, beta-D-glucosidase, which hydrolyses PHBOG to yield PHB, was also located in the cytosol. These results suggest that PHB glucosylated in the cytosol is transported into the vacuole to be stored in a large quantity under protection from beta-D-glucosidase in shikonin non-producing cells, until utilization as a precursor upon induction of shikonin biosynthesis.