Fiore Alessia, Dall'osto Luca, Fraser Paul D, Bassi Roberto, Giuliano Giovanni
Ente per le Nuove tecnologie, l'Energia e l'Ambiente (ENEA), Dipartimento Biotecnologie, Centro Ricerche Casaccia, C.P. 2400, Roma 00100, Italy.
FEBS Lett. 2006 Aug 21;580(19):4718-22. doi: 10.1016/j.febslet.2006.07.055. Epub 2006 Jul 26.
The first dedicated step in plant xanthophyll biosynthesis is carotenoid hydroxylation. In Arabidopsis thaliana, this reaction is performed by both heme (LUT1 and LUT5) and non-heme (CHY1 and CHY2) hydroxylases. No mutant completely abolishing alpha- or beta-carotene hydroxylation has been described to date. We constructed double and triple mutant combinations in CHY1, CHY2, LUT1, LUT5 and LUT2 (lycopene epsilon-cyclase). In chy1chy2lut2, 80% of leaf carotenoids is represented by beta-carotene. In chy1chy2lut5, beta-carotene hydroxylation is completely abolished, while hydroxylation of the beta-ring of alpha-carotene is still observed. The data are consistent with a role of LUT5 in beta-ring hydroxylation, and with the existence of an additional hydroxylase, acting on the beta-ring of alpha-, but not beta-carotene.
植物叶黄素生物合成的首个专门步骤是类胡萝卜素羟基化。在拟南芥中，该反应由血红素（LUT1和LUT5）和非血红素（CHY1和CHY2）羟化酶共同完成。迄今为止，尚未描述出完全消除α-或β-胡萝卜素羟基化的突变体。我们构建了CHY1、CHY2、LUT1、LUT5和LUT2（番茄红素ε-环化酶）的双突变体和三突变体组合。在chy1chy2lut2中，80%的叶片类胡萝卜素由β-胡萝卜素代表。在chy1chy2lut5中，β-胡萝卜素羟基化被完全消除，而仍可观察到α-胡萝卜素β-环的羟基化。这些数据与LUT5在β-环羟基化中的作用一致，并且与存在一种额外的羟化酶相符，该羟化酶作用于α-胡萝卜素的β-环，而非β-胡萝卜素的β-环。
