Jung Suk-Chae, Kim Woohyun, Park Sung Chul, Jeong Jinkil, Park Myung Keun, Lim Soohwan, Lee Yeon, Im Wan-Taek, Lee Jun Hyoung, Choi Giltsu, Kim Sun Chang
Department of Biological Sciences, KAIST, Daejeon 305-701, Republic of Korea.
KAIST Institute for Biocentury, KAIST, Daejeon, 305-701, Republic of Korea.
Plant Cell Physiol. 2014 Dec;55(12):2177-88. doi: 10.1093/pcp/pcu147. Epub 2014 Oct 14.
Ginseng is a medicinal herb that requires cultivation under shade conditions, typically for 4-6 years, before harvesting. The principal components of ginseng are ginsenosides, glycosylated tetracyclic terpenes. Dammarene-type ginsenosides are classified into two groups, protopanaxadiol (PPD) and protopanaxatriol (PPT), based on their hydroxylation patterns, and further diverge to diverse ginsenosides through differential glycosylation. Three early enzymes, dammarenediol-II synthase (DS) and two P450 enzymes, protopanaxadiol synthase (PPDS) and protopanaxatriol synthase (PPTS), have been reported, but glycosyltransferases that are necessary to synthesize specific ginsenosides have not yet been fully identified. To discover glycosyltransferases responsible for ginsenoside biosynthesis, we sequenced and assembled the ginseng transcriptome de novo and characterized two UDP-glycosyltransferases (PgUGTs): PgUGT74AE2 and PgUGT94Q2. PgUGT74AE2 transfers a glucose moiety from UDP-glucose (UDP-Glc) to the C3 hydroxyl groups of PPD and compound K to form Rh2 and F2, respectively, whereas PgUGT94Q2 transfers a glucose moiety from UDP-Glc to Rh2 and F2 to form Rg3 and Rd, respectively. Introduction of the two UGT genes into yeast together with PgDS and PgPPDS resulted in the de novo production of Rg3. Our results indicate that these two UGTs are key enzymes for the synthesis of ginsenosides and provide a method for producing specific ginsenosides through yeast fermentation.
人参是一种药草，需要在遮荫条件下种植，通常种植4至6年后才能收获。人参的主要成分是人参皂苷，即糖基化的四环萜类化合物。达玛烷型人参皂苷根据其羟基化模式可分为两组，原人参二醇（PPD）和原人参三醇（PPT），并通过不同的糖基化进一步衍生出多种人参皂苷。已报道了三种早期酶，即达玛烯二醇-II合成酶（DS）和两种细胞色素P450酶，原人参二醇合成酶（PPDS）和原人参三醇合成酶（PPTS），但尚未完全鉴定出合成特定人参皂苷所需的糖基转移酶。为了发现负责人参皂苷生物合成的糖基转移酶，我们对人参转录组进行了从头测序和组装，并鉴定了两种尿苷二磷酸糖基转移酶（PgUGTs）：PgUGT74AE2和PgUGT94Q2。PgUGT74AE2分别将来自尿苷二磷酸葡萄糖（UDP-Glc）的葡萄糖部分转移到PPD和化合物K的C3羟基上，形成Rh2和F2，而PgUGT94Q2分别将来自UDP-Glc的葡萄糖部分转移到Rh2和F2上，形成Rg3和Rd。将这两个UGT基因与PgDS和PgPPDS一起导入酵母中，导致了Rg3的从头合成。我们的结果表明，这两种UGT是合成人参皂苷的关键酶，并提供了一种通过酵母发酵生产特定人参皂苷的方法。
