Punyasiri P A N, Abeysinghe I S B, Kumar V, Treutter D, Duy D, Gosch C, Martens S, Forkmann G, Fischer T C
Biochemistry Division, Tea Research Institute of Sri Lanka, Talawakelle, Sri Lanka.
Arch Biochem Biophys. 2004 Nov 1;431(1):22-30. doi: 10.1016/j.abb.2004.08.003.
Leaves of tea (Camellia sinensis L.) contain extraordinary large amounts of (-)-epigallocatechin, (-)-epicatechin, (+)-gallocatechin, and (+)-catechin and derivatives of these compounds that show positive effects on human health. The health-promoting effects of flavan 3-ols, especially those of green tea, are of scientific and public interest. Furthermore, they play a crucial role in defense against pathogens of tea. Therefore, biosynthesis of these flavonoid compounds was investigated. The anthocyanidin reductase enzyme recently described from Arabidopsis and Medicago was shown to be present in tea with very high activity and produces epicatechin as well as epigallocatechin from the respective anthocyanidins, thus explaining the very high contents of these compounds. A strong combined dihydroflavonol 4-reductase/leucoanthocyanidin 4-reductase activity was demonstrated and catalyzes the key steps in catechin and gallocatechin formation. Together with the enzyme activities and substrate specificities of the preceding enzymatic reactions, the biosynthesis of the most prominent flavonoids of tea is elucidated.
茶树（Camellia sinensis L.）的叶子含有大量的（-）-表没食子儿茶素、（-）-表儿茶素、（+）-没食子儿茶素和（+）-儿茶素以及这些化合物的衍生物，它们对人体健康有积极影响。黄烷-3-醇，尤其是绿茶中的黄烷-3-醇的健康促进作用，具有科学和公众关注价值。此外，它们在茶树抵御病原体方面起着关键作用。因此，对这些类黄酮化合物的生物合成进行了研究。最近在拟南芥和苜蓿中发现的花青素还原酶在茶树中具有很高的活性，能从相应的花青素中产生表儿茶素和表没食子儿茶素，从而解释了这些化合物的高含量。已证明存在很强的二氢黄酮醇还原酶/无色花青素还原酶联合活性，它催化儿茶素和没食子儿茶素形成的关键步骤。结合前面酶促反应的酶活性和底物特异性，阐明了茶树中最主要类黄酮的生物合成过程。
