earticle

영어

Heterogeneity of plant secondary metabolites with similar structures but different bioactivities is a widely existing phenomenon in nature, and rational manipulation of bioproducts heterogeneity is a challenge to biochemical engineers. As reported so far, many individual ginsenosides possess different or even opposite pharmacological activities. However, there is lack of reports on the heterogeneity engineering for plant secondary metabolites in spite of the significance of such investigations. According to the minor difference of chemical structures of various ginsenosides, we propose that there may exist a close relationship between ginsenoside heterogeneity and the hydroxylation of ginsenoside aglycones and glycosylation of individual ginsenosides. For the rational regulation of ginsenoside heterogeneity, it is critical to study the unknown enzymes of ginsenoside glucosyltransferase and hydroxylase as well as their activity induction. This work focused on glucosyltransferase and hydroxylase as well as heterogeneity of ginsenosides in cell cultures of Panax notoginseng, which is a traditional and valuable Chinese medicinal herb. A glucosyltransferase, which catalyzes the synthesis of ginsenoside Rb1 from Rd by glucosylation, named UDPG:ginsenoside Rd glucosyltransferase (UGRdGT), was purified from cell cultures of P. notoginseng. A hydroxylase, catalyzing the synthesis of protopanaxatriol from protopanaxadiol, called as protopanaxadiol-6-hydroxylase (P6H), was also discovered. Manipulation of external calcium concentration and phenobenbarbital addition was found useful to induce the enzyme activity of UGRdGT and P6H and to alter the ginsenoside biosynthesis and heterogeneity. The information obtained will also be helpful to the manipulation and efficient production of other heterogeneous secondary metabolites by cell cultures.