茶树酯型儿茶素生物合成及水解途径研究进展

Advances in Research of Biosynthesis and Hydrolysis Pathways of Gallated Catechins in Camellia sinensis

茶树酯型儿茶素对于茶叶加工产品品质的影响及人类健康的药理功效均高于非酯型儿茶素。酯型儿茶素合成及水解途径及分子调控机理,既是长期困扰茶业界的重点难题,也是富含原花青素(PAs)或缩合单宁(CAs)植物如葡萄、柿子的未解科学问题之一。作者在文中介绍了茶树酯型儿茶素合成及水解途径研究上取得的进展,儿茶素的没食子酰基化过程与水解单宁合成具有相似性;没食子酰基葡糖糖(βG)是它们合成的酰基供体,与葡萄糖基转移酶(UGGT)和没食子酰基转移酶(ECGT)等有关;在茶树中酯型儿茶素很容易被水解酶(GCH)水解为没食子酸和非酯型儿茶素。此外,还综述了国际上有关flavan-3-ols的合成、聚合、糖苷化和甲基化研究进展。

Gallated catechins have stronger effects than non-galloylated catechins, both on the product quality in tea processing and the pharmacological efficacy to human beings. The biosynthesis and hydrolysis pathways as well as molecular regulation mechanism of gallated catechins, have been a key problem that perplexes tea industry since long, and also been an unsolved scientific issue in Vitis vinifera or Diospyros kaki which is riched in procyanidins （PAs） or condensed tannins （CAs）. Advances in research of biosynthetic and hydrolysis pathways of gallated catechins in Camellia sinensis by this research group were reviewed. The results showed that the means of catechin galloylation were similar to that of hydrolyzable tannin synthesis, in which, β-glucogallin （βG） acted as an acyl donor, and which involved two enzymes, UDP-glucose： galloyl-1-O-β-D- glucosyltransferase （UGGT） and epicatechin：1-O-galloyl-β-D-glucose O-galloyltransferase （ECGT）. Besides, the galloylated catechins could be hydrolyzed to ungalloylated catechins and gallic acid with the galloylated catechins hydrolase （GCH） action in Camellia sinensis. In addition, recent progress in biosynthesis, polymerization, glycosylation and methylation of flavan-3-ols in the world was also reviewed.