葱属植物S-烷(烯)基半胱氨酸亚砜代谢途径研究进展

Research progress on metabolic pathway of S-alk(en)ylcysteine sulfoxides in Allium

关键词:  葱属植物, S-烷(烯)基半胱氨酸亚砜, 蒜氨酸酶, 风味物质, 代谢途径

Key words:  Allium, S-alk(en)ylcysteine sulfoxide, alliinase, flavor compound, metabolic pathway

摘要:

葱属植物是被子植物中最大的属之一,包括大蒜、洋葱、大葱、韭菜等多种具有独特辛辣风味的蔬菜作物。S-烷(烯)基半胱氨酸亚砜是葱属植物特有的次生代谢产物,是葱属植物各种挥发性含硫化合物的前体物质,由于其赋予葱属植物独特的辛辣风味和药用价值,因此研究葱属植物S-烷(烯)基半胱氨酸亚砜的代谢途径具有重要意义。在葱属植物中已发现7种S-烷(烯)基半胱氨酸亚砜,这些S-烷(烯)基半胱氨酸亚砜主要在叶片中先经谷胱甘肽途径合成,再转运到鳞茎等贮藏器官的细胞质中积累。目前,关于葱属植物S-烷(烯)基半胱氨酸亚砜降解的研究较多,而S-烷(烯)基半胱氨酸亚砜生物合成的研究则较少。S-烷(烯)基半胱氨酸亚砜是植物硫代谢的下游产物,上游涉及含硫化合物的吸收、转运、半胱氨酸和谷胱甘肽的代谢等过程,这些代谢过程的变化可能影响S-烷(烯)基半胱氨酸亚砜生物合成。今后,应加强以下两方面的研究:一方面,继续克隆鉴定S-烷(烯)基半胱氨酸亚砜生物合成途径中的关键酶基因,并研究其功能; 另一方面,加强葱属植物硫代谢的研究,为研究S-烷(烯)基半胱氨酸亚砜生物合成的调控奠定基础。该研究结果为深入解析葱属植物S-烷(烯)基半胱氨酸亚砜的代谢途径以及利用分子育种技术调控葱属植物的风味提供了参考。

Abstract:

Allium, including garlic, onion, green Chinese onion, Chinese chive and other important vegetable crops with unique spicy flavor, is one of the largest genera of angiosperms. S-alk(en)ylcysteine sulfoxides, the unique secondary metabolites of Allium, which giving Allium spicy flavor and medicinal value, are the precursors of various volatile sulfur compounds. Therefore, it is of great significance to study the metabolic pathway of S-alk(en)ylcysteine sulfoxides in Allium. Seven S-alk(en)ylcysteine sulfoxides have been found in Allium plants. These S-alk(en)ylcysteine sulfoxides are mainly synthesized in leaves through glutathione pathway, and then transported to the cytoplasm of storage organs such as bulbs for accumulation. At present, there are many studies on the catabolism of S-alk(en)ylcysteine sulfoxides in Allium, while few studies on the biosynthesis of S-alk(en)ylcysteine sulfoxides. Only two biosynthetic enzymes, γ-glutamyl transpeptidase(GGT)and flavin-containing monooxygenase(FMO), have been confirmed at the molecular level. In addition, S-alk(en)ylcysteine sulfoxides are the downstream products of plant sulfur metabolism. The upstream of S-alk(en)ylcysteine sulfoxide metabolism involves the absorption and transport of sulfur-containing compounds, the metabolism of cysteine and glutathione, and the changes of these metabolic processes may also affect the biosynthesis of S-alk(en)ylcysteine sulfoxides. With the rapid development of omics technology, genomics, transcriptomics and metabolomics have been applied in the study of Allium plants, especially the completion of garlic genome sequence assembly, which provides great convenience for the study of S-alk(en)ylcysteine sulfoxides metabolism pathway in Allium plants. Two aspects of research should be strengthened in the future: One is to continue to clone and identify the key enzyme genes in the biosynthesis pathway of S-alk(en)ylcysteine sulfoxides and study their functions; another is to strengthen the study of sulfur metabolism in Allium plants, so as to lay a foundation for the study of the regulation of S-alk(en)ylcysteine sulfoxides biosynthesis. These studies will provide a reference for further analyzing the metabolic pathway of S-alk(en)ylcysteine sulfoxides in Allium and regulating the flavor of Allium by molecular breeding technology.