The decisive step in betaxanthin biosynthesis is a spontaneous reaction
The decisive step in betaxanthin biosynthesis is a spontaneous reaction
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DOI：
10.1104/pp.119.4.1217
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发表时间：
1999-04-01
期刊：
影响因子：
7.4
通讯作者：
Strack, D
中科院分区：
文献类型：
--
作者：
Schliemann, W;Kobayashi, N;Strack, D
实验证实，乙二胺键的形成是一个自发反应，因为试图找到一种酶来催化甜菜黄素生物合成的最后一个决定性步骤，即乙二胺的形成，但失败了。将不同氨基酸添加到甜菜毛状根培养物中。普通甜菜)表明，所有氨基酸(S型和R型)都会导致相应的甜菜黄质。在这一过程中，我们既没有观察到氨基酸的特异性，也没有观察到立体选择性。此外，通过添加苯丙氨酸解氨酶抑制剂2-氨基吲哚-2-磷酸来提高内源苯丙氨酸的水平，可以得到苯丙氨酸衍生的甜菜黄素。饲用甜菜(B.volgaris L.subsp.)下胚轴添加氨基酸或2-氨基吲哚-2-磷酸Volgaris“AlTamo”)植物导致了同样的结果。此外，向这些下胚轴提供环-3-(3，4-二羟基苯基)-丙氨酸(环-多巴)导致甜菜素的形成，这表明甜菜青素形成的决定性步骤是自发进行的。最后，对蚕豆(Vicia Faba L.)已知的幼苗积累了高水平的多巴，但不合成甜菜黄质，导致了多巴黄质的形成。这些结果表明，在植物中，倍他胺酸与氨基酸(可能包括环多巴或胺)的缩合反应是自发的，而不是酶催化的反应。
Experiments were performed to confirm that the aldimine bond formation is a spontaneous reaction, because attempts to find an enzyme catalyzing the last decisive step in betaxanthin biosynthesis, the aldimine formation, failed. Feeding different amino acids to betalain-forming hairy root cultures of yellow beet (Beta vulgaris L. subsp. vulgaris "Golden Beet") showed that all amino acids (S- and R-forms) led to the corresponding betaxanthins. We observed neither an amino acid specificity nor a stereoselectivity in this process. In addition, increasing the endogenous phenylalanine (Phe) level by feeding the Phe ammonia-lyase inhibitor 2-aminoindan 2-phosphonic acid yielded the Phe-derived betaxanthin. Feeding amino acids or 2-aminoindan 2-phosphonic acid to hypocotyls of fodder beet (B. volgaris L. subsp. volgaris "Altamo") plants led to the same results. Furthermore, feeding cyclo-3-(3,4-dihydroxyphenyl)-alanine (cyclo-Dopa) to these hypocotyls resulted in betanidin formation, indicating that the decisive step in betacyanin formation proceeds spontaneously. Finally, feeding betalamic acid to broad bean (Vicia faba L.) seedlings, which are known to accumulate high levels of Dopa but do not synthesize betaxanthins, resulted in the formation of dopaxanthin. These results indicate that the condensation of betalamic acid with amino acids (possibly including cyclo-Dopa or amines) in planta is a spontaneous, not an enzyme-catalyzed reaction.