Detection of UDP-glucose:cyclo-DOPA 5-O-glucosyltransferase activity in four o'clocks (Mirabilis jalapa L.)
Detection of UDP-glucose:cyclo-DOPA 5-O-glucosyltransferase activity in four o'clocks (Mirabilis jalapa L.)
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DOI：
10.1016/j.febslet.2004.04.097
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发表时间：
2004-06-18
期刊：
影响因子：
3.5
通讯作者：
Ozeki, Y
中科院分区：
文献类型：
--
作者：
Sasaki, N;Adachi, T;Ozeki, Y
虽然已经推测了甜菜红素的生物合成途径，但大多数催化步骤还没有得到确认或生化证据的证明。在假设的途径中，甜菜素的葡萄糖部分连接到苷元，甜菜素，因为已经报道了产生甜菜素的葡萄糖转移酶(GT)活性，并分离了它的cDNA。然而，另一种合成β-花青素的方法是通过GT作用于5，6-二羟基吲哚-2-羧酸(环-DOPA)，然后产物与β-氨基甲酸缩合而成。在这里，我们表明，GT活性作用于甜菜青素合成途径中的环-多巴。从紫茉莉(Mirabilis Jalapa L.)花瓣中提取的粗提物与环多巴和UDP-葡萄糖混合。用磷酸停止反应后，产物与倍他拉米酸发生化学反应。在最终的反应混合物中，高效液相分析证实了甜菜素的生成，证明了环多巴5-O-葡萄糖基转移酶的活性。这种活性与四朵花发育过程中甜菜素的积累有关，在另外五种着丝子植物中也检测到这种活性。这些结果表明，甜菜碱的葡萄糖部分是在环多巴步骤中引入的，然后与甜菜碱苷元缩合，而不是在甜菜碱苷元步骤中引入。(C)2004年欧洲生化学会联合会。爱思唯尔出版，版权所有。
Although a pathway for betacyanin biosynthesis has been postulated, most of the catalytic steps have not yet been identified or demonstrated with biochemical evidence. In the postulated pathway, the glucose moiety of betanin is conjugated to the aglycone, betanidin, because the glucosyltransferase (GT) activity that produces betanin has been reported and its cDNA isolated. However, another pathway for betacyanin biosynthesis is proposed in which betanin is formed by GT acting at the 5,6-dihydroxyindoline-2-carboxylic acid (cyclo-DOPA) step, followed by condensation of the product with betalamic acid. Here, we show that GT activity acts upon cycla-DOPA in the betacyanin synthetic pathway. A crude extract from the petals of four o'clocks (Mirabilis jalapa L.) was mixed with cyclo-DOPA and UDP-glucose. After the reaction was stopped with phosphoric acid, the product was chemically reacted with betalamic acid. In the final reaction mixture, betanin formation was confirmed by HPLC analysis, demonstrating cyclo-DOPA 5-O-glucosyltransferase activity. This activity was correlated with the accumulation of betanin during the development of four o'clock flowers and was detected in another five species of Centrospermae. These results indicate that the glucose moiety of betanin is introduced at the cyclo-DOPA step, which is followed by condensation with betalamic acid, and not at the betanidin aglycone step. (C) 2004 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.