[Expression, subcellular localization and characterization of dammarenediol-â ¡ synthase of Panax ginseng in Saccharomyces cerevisiae].

To study the expression and subcellular localization of recombinant dammarenediol-Ⅱ synthase (DS) in Saccharomyces cerevisiae, the dammarenediol-Ⅱ synthase gene ds was cloned from Panax ginseng, and the gene ds was fused with the gene of green fluorescent protein to obtain the fusion gene ds-gfp. The recombinant expression plasmids pESC-HIS-DS and pESC-HIS-DS-GFP were constructed and transformed into S. cerevisiae INVSc1 to obtain recombinant strains INVSc1-DS and INVSc1-DS-GFP. Microsomes of recombinant strains were prepared by differential centrifugation and observed by fluorescence microscope. The green fluorescence was only detected in INVSc1-DS-GFP microsomes, which indicated that DS was a membrane protein. It was also proved that dammarenediol-Ⅱ was produced from the cyclization of 2,3-oxidosqualene catalyzed by DS through in vitro enzymatic reaction. In addition, our results revealed that the fusion expression of ds with gfp significantly improved the production of dammarenediol-Ⅱ from 7.53 mg·g(-1) to 12.24 mg·g(-1). This study provides a new strategy in the optimization of the pathway of ginsenosides biosynthesis in S.cerevisiae.

[The basic strategies and research advances in the studies on glycosyltransferases involved in ginsenoside biosynthesis].

Traditional herbal medicines, Panax ginseng, Panax quinquefolium and Panax notoginseng, attract our attention for their extensive and powerful pharmacological activities. Ginsenosides are the main active constituents of these medicinal herbs. The related glycosyltransferases involved in ginsenoside biosynthesis are the key enzymes which catalyze the last important step. Modification of ginsenoside aglycones by glycosyltransferases produces the complexity and diversity of ginsenosides, which have more extensive pharmacological activity. At present, ginsenoside aglycones and compound K have been obtained by synthetic biology. As the last step of ginsenoside biosynthesis, glycosylation of ginsenoside aglycones has been studied intensively in recent years. This review summarizes the basic strategies and research advances in studies on glycosyltransferases involved in ginsenoside biosynthesis, which is expected to lay the theoretical foundation for the in-depth research of biosynthetic pathway of ginsenosides and their production by synthetic biology.

[Primary study on quality standard of carbonizing drug characteristic of ginger carbon].

OBJECTIVE: To establish the quality standard for carbonizing drug characteristic of ginger carbon. METHOD: Gingers and different carbonized gingers were compared by the absorption of pigment, tannin content, pH, mouth's coagulation time and bleeding time. RESULT: The study resulted in the recommended carbonizing standard that the absorption capacity shall not be less than 7.50 mg x g(-1) for methylene blue, the tannin content shall not be less than 2.103 mg x g(-1), the pH shall be (5.50 +/- 0.10), and coagulation time and bleeding time shall be the shorter the better. CONCLUSION: The established assessment standard for carbonizing drug characteristic of ginger carbon is reasonable, easily operated and feasible.