Iridoid-specific Glucosyltransferase from Gardenia jasminoides
Iridoid-specific Glucosyltransferase from Gardenia jasminoides
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DOI：
10.1074/jbc.m111.242586
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发表时间：
2011-09-16
影响因子：
4.8
通讯作者：
Mizukami, Hajime
中科院分区：
文献类型：
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作者：
Nagatoshi, Mai;Terasaka, Kazuyoshi;Mizukami, Hajime
环烯醚萜类化合物是高等植物中分布最广的次生代谢产物之一。它们是多种药用植物中的活性成分，也是单萜吲哚生物碱和喹啉生物碱生物合成的关键中间体。虽然大多数环烯醚萜以1-O-葡萄糖苷的形式存在，但生物合成途径中的葡萄糖基化步骤仍然不清楚。我们从栀子中分离到一个编码UDP葡萄糖：环烯醚萜葡萄糖基转移酶（UGT 85 A24）的cDNA。UGT 85 A24优先使7-脱氧马钱精和京尼平的1-O-羟基葡糖基化，但仅对马钱精表现出弱活性，对7-脱氧马钱酸没有活性。这表明，在京尼平苷的生物合成途径中，京尼平苷是一种主要的环烯醚萜类化合物。jasminoides，葡萄糖基化发生在7-脱氧loganetic酸甲基化之后。UGT 85 A24对环烯醚萜苷元以外的任何受体底物显示出可忽略的活性。因此，UGT 85 A24对环烯醚萜苷元具有显著的特异性。在茉莉酸甲酯处理的G. jasminoides中环烯醚萜的积累有关。茉莉果实
Iridoids are one of the most widely distributed secondary metabolites in higher plants. They are pharmacologically active principles in various medicinal plants and key intermediates in the biosynthesis of monoterpenoid indole alkaloids as well as quinoline alkaloids. Although most iridoids are present as 1-O-glucosides, the glucosylation step in the biosynthetic pathway has remained obscure. We isolated a cDNA coding for UDPglucose: iridoid glucosyltransferase (UGT85A24) from Gardenia jasminoides. UGT85A24 preferentially glucosylated the 1-O-hydroxyl group of 7-deoxyloganetin and genipin but exhibited only weak activity toward loganetin and no activity toward 7-deoxyloganetic acid. This suggests that, in the biosynthetic pathway of geniposide, a major iridoid compound in G. jasminoides, glucosylation occurs after methylation of 7-deoxyloganetic acid. UGT85A24 showed negligible activity toward any acceptor substrates other than iridoid aglycones. Thus, UGT85A24 has a remarkable specificity for iridoid aglycones. The mRNA level of UGT85A24 overlaps with the marked increase in genipin glucosylation activity in the methyl jasmonate-treated cell cultures of G. jasminoides and is related to iridoid accumulation in G. jasminoides fruits.