Molecular cloning, substrate specificity of the functionally expressed dihydroflavonol 4-reductases from Malus domestica and Pyrus communis cultivars and the consequences for flavonoid metabolism
Molecular cloning, substrate specificity of the functionally expressed dihydroflavonol 4-reductases from Malus domestica and Pyrus communis cultivars and the consequences for flavonoid metabolism
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DOI：
10.1016/s0003-9861(03)00013-4
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发表时间：
2003-04-15
影响因子：
3.9
通讯作者：
Forkmann, G
中科院分区：
文献类型：
--
作者：
Fischer, TC;Halbwirth, H;Forkmann, G
用双加氧酶抑制剂调环酮-Ca处理导致苹果（Malus acutica）和梨（Pyrus communis）叶的类黄酮代谢发生重大变化。观察到不寻常的3-脱氧类黄酮的积累，这与对火疫病的增强抗性有关。这一途径中的关键步骤是减少黄烷酮。来自叶子的粗提取物能够进行该反应。之前有证据表明某些植物的DFR酶具有额外的黄烷酮4-还原酶（FNR）活性。DFR酶的这种FNR活性在此通过酶的异源表达来证明。苹果和梨异源表达的DFR/FNR酶在底物特异性上具有明显的差异，尽管氨基酸序列只有微小的差异。动力学研究表明，二氢黄酮醇通常是首选的底物。然而，通过观察到的底物特异性，可以解释应用调环酸钙后体内3-脱氧黄酮的发生。(C)2003 Elsevier Science（美国）。All rights reserved.
Treatment with the dioxygenase inhibitor prohexadione-Ca leads to major changes in the flavonoid metabolism of apple (Malus domestica) and pear (Pyrus communis) leaves. Accumulation of unusual 3-deoxyflavonoids is observed, which have been linked to an enhanced resistance toward fire blight. The committed step in this pathway is the reduction of flavanones. Crude extracts from leaves are able to perform this reaction. There was previous evidence that DFR enzymes of certain plants possess additional flavanone 4-reductase (FNR) activity. Such an FNR activity of DFR enzymes is proved here by heterologous expression of the enzymes. The heterologously expressed DFR/FNR enzymes of Malus and Pyrus possess distinct differences in substrate specificities despite only minor differences of the amino acid sequences. Kinetic studies showed that dihydroflavonols generally are the preferred substrates.' However, with the observed substrate specificities the occurrence of 3-deoxyflavonoids in vivo after application of prohexadione-Ca can be explained. (C) 2003 Elsevier Science (USA). All rights reserved.