Seki Hikaru, Tamura Keita, Muranaka Toshiya
Department of Biotechnology, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita Osaka, 565-0871 Japan
Department of Biotechnology, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita Osaka, 565-0871 Japan.
Plant Cell Physiol. 2015 Aug;56(8):1463-71. doi: 10.1093/pcp/pcv062. Epub 2015 May 6.
The recent spread of next-generation sequencing techniques has facilitated transcriptome analyses of non-model plants. As a result, many of the genes encoding enzymes related to the production of specialized metabolites have been identified. Compounds derived from 2,3-oxidosqualene (the common precursor of sterols, steroids and triterpenoids), a linear compound of 30 carbon atoms produced through the mevalonate pathway, are called triterpenes. These include essential sterols, which are structural components of biomembranes; steroids such as the plant hormones, brassinolides and the toxin in potatoes, solanine; as well as the structurally diverse triterpenoids. Triterpenoids containing one or more sugar moieties attached to triterpenoid aglycones are called triterpenoid saponins. Triterpenoid saponins have been shown to have various medicinal properties, such as anti-inflammatory, anticancerogenic and antiviral effects. This review summarizes the recent progress in gene discovery and elucidates the biochemical functions of biosynthetic enzymes in triterpenoid saponin biosynthesis. Special focus is placed on key players in generating the structural diversity of triterpenoid saponins, cytochrome P450 monooxygenases (P450s) and the UDP-dependent glycosyltransferases (UGTs). Perspectives on further gene discovery and the use of biosynthetic genes for the microbial production of plant-derived triterpenoid saponins are also discussed.
近年来，新一代测序技术的广泛应用推动了非模式植物转录组分析的发展。因此，许多与特殊代谢产物合成相关的酶编码基因得以鉴定。由2,3-氧化角鲨烯（甾醇、类固醇和三萜类化合物的共同前体）衍生而来的化合物，是通过甲羟戊酸途径产生的一种含30个碳原子的线性化合物，被称为三萜类化合物。这些化合物包括作为生物膜结构成分的必需甾醇；类固醇，如植物激素油菜素内酯和马铃薯中的毒素茄碱；以及结构多样的三萜类化合物。在三萜类苷元上连接有一个或多个糖基部分的三萜类化合物被称为三萜皂苷。三萜皂苷已被证明具有多种药用特性，如抗炎、抗癌和抗病毒作用。本综述总结了基因发现的最新进展，并阐明了三萜皂苷生物合成中生物合成酶的生化功能。特别关注了在产生三萜皂苷结构多样性方面的关键参与者，细胞色素P450单加氧酶（P450s）和UDP依赖性糖基转移酶（UGTs）。还讨论了进一步基因发现的前景以及利用生物合成基因进行微生物生产植物源三萜皂苷的问题。
