An Aromatic Farnesyltransferase Functions in Biosynthesis of the Anti-HIV Meroterpenoid Daurichromenic Acid
An Aromatic Farnesyltransferase Functions in Biosynthesis of the Anti-HIV Meroterpenoid Daurichromenic Acid
复制标题
DOI：
10.1104/pp.18.00655
复制
发表时间：
2018-10-01
期刊：
影响因子：
7.4
通讯作者：
Taura, Futoshi
中科院分区：
文献类型：
--
作者：
Saeki, Haruna;Hara, Ryota;Taura, Futoshi
满山红产生蝙蝠葛色烯酸，一种抗艾滋病病毒meroterpenoid，通过氧化环化的法尼基基团的grifolic酸。异戊烯基转移酶（prenyltransferase，PT）是植物特化代谢中的一种法尼基转移酶。在这项研究中，我们证明了灰叶酸的类异戊二烯部分来自质体中发生的2-C-甲基-D-β-4-磷酸途径。我们探索了质体定位的PT同源物的候选序列，并鉴定了该PT的cDNA RdPT 1，它与已知的芳香族PT具有中等序列相似性。RdPT 1仅在腺鳞中表达，其中蝙蝠葛色烯酸积累。此外，该基因产物被靶向植物细胞中的质体。重组RdPT 1区域特异性合成grifolic酸从orsellinic酸和法呢基二磷酸，表明RdPT 1是法呢基转移酶参与蝙蝠葛色烯酸的生物合成。这种酶严格首选orsellinic酸作为异戊烯受体，而它有一个宽松的异戊烯供体结构的特异性，也接受香叶基和香叶基香叶基二磷酸合成异戊烯链类似物grifolic酸的效率适中。这种广泛的特异性是RdPT 1的独特催化特征，其在植物中的次级代谢芳香族PT之间不共享。我们讨论了不寻常的底物偏好的RdPT 1使用的分子建模方法。RdPT 1的生物化学性质以及定位表明，该酶与先前鉴定的daurichromenic acid synthase合作在腺鳞中产生部分萜类化合物，可能用于R.蝙蝠葛属植物
Rhododendron dauricum produces daurichromenic acid, an anti-HIV meroterpenoid, via oxidative cyclization of the farnesyl group of grifolic acid. The prenyltransferase (PT) that synthesizes grifolic acid is a famesyltransferase in plant specialized metabolism. In this study, we demonstrated that the isoprenoid moiety of grifolic acid is derived from the 2-C-methyl-D-erythritol-4-phosphate pathway that takes place in plastids. We explored candidate sequences of plastid-localized PT homologs and identified a cDNA for this PT, RdPT1, which shares moderate sequence similarity with known aromatic PTs. RdPT1 is expressed exclusively in the glandular scales, where daurichromenic acid accumulates. In addition, the gene product was targeted to plastids in plant cells. The recombinant RdPT1 regiospecifically synthesized grifolic acid from orsellinic acid and famesyl diphosphate, demonstrating that RdPT1 is the farnesyltransferase involved in daurichromenic acid biosynthesis. This enzyme strictly preferred orsellinic acid as a prenyl acceptor, whereas it had a relaxed specificity for prenyl donor structures, also accepting geranyl and geranylgeranyl diphosphates with modest efficiency to synthesize prenyl chain analogs of grifolic acid. Such a broad specificity is a unique catalytic feature of RdPT1 that is not shared among secondary metabolic aromatic PTs in plants. We discuss the unusual substrate preference of RdPT1 using a molecular modeling approach. The biochemical properties as well as the localization of RdPT1 suggest that this enzyme produces meroterpenoids in glandular scales cooperatively with previously identified daurichromenic acid synthase, probably for chemical defense on the surface of R. dauricum plants.