Steffan N, Grundmann A, Yin W-B, Kremer A, Li S-M
Philipps-Universität Marburg, Institut für Pharmazeutische Biologie, Deutschhausstrasse 17A, 35037 Marburg, Germany.
Curr Med Chem. 2009;16(2):218-31. doi: 10.2174/092986709787002772.
Prenylated indole derivatives are hybrid natural products containing both aromatic and isoprenoid moieties and are widely spread in plants, fungi and bacteria. Some of these complex natural products, e.g. the ergot alkaloids ergotamine and fumigaclavine C as well as the diketopiperazine derivative fumitremorgin C and its biosynthetic precursors tryprostatin A and B, show a wide range of biological and pharmacological activities. Prenyl transfer reactions catalysed by prenyltransferases represent key steps in the biosynthesis of these compounds and often result in formation of products which possess biological activities distinct from their non-prenylated precursors. Recently, a series of putative indole prenyltransferase genes could be identified in the genome sequences of different fungal strains including Aspergillus fumigatus. The gene products show significant sequence similarities to dimethylallyltryptophan synthases from fungi. We have cloned and overexpressed six of these genes, fgaPT1, fgaPT2, ftmPT1, ftmPT2, 7-dmats and cdpNPT from A. fumigatus in E. coli and S. cerevisiae. The overproduced enzymes were characterised biochemically. Three additional prenyltransferases, DmaW-Cs, TdiB and MaPT were identified and characterised in a Clavicipitalean fungus, Aspergillus nidulans and Malbranchea aurantiaca, respectively. Sequence analysis and alignments with known aromatic prenyltransferases as well as phylogenetic analysis revealed that these enzymes belong to a new group of "aromatic prenyltransferases". They differ clearly from membrane-bound aromatic prenyltransferases from different sources and soluble prenyltransferases from bacteria. The characterised enzymes are soluble proteins, catalyse different prenyl transfer reactions on indole moieties of various substrates and do not require divalent metal ions for their enzymatic reactions. All of the enzymes accepted only dimethylallyl diphosphate as prenyl donor. On the other hand, they showed broad substrate specificity towards their aromatic substrates. Diverse tryptophan derivatives and tryptophan-containing cyclic dipeptides were accepted by these enzymes, providing a new strategy for convenient production of biologically active substances, e.g. by chemoenzymatic synthesis.
异戊烯基化吲哚衍生物是一类同时含有芳香族和类异戊二烯部分的杂合天然产物，广泛存在于植物、真菌和细菌中。其中一些复杂的天然产物，如麦角生物碱麦角胺和烟曲霉棒曲霉素C，以及二酮哌嗪衍生物烟曲霉震颤素C及其生物合成前体曲古抑菌素A和B，具有广泛的生物学和药理活性。异戊烯基转移酶催化的异戊烯基转移反应是这些化合物生物合成中的关键步骤，常常导致形成具有与其未异戊烯基化前体不同生物活性的产物。最近，在包括烟曲霉在内的不同真菌菌株的基因组序列中鉴定出了一系列假定的吲哚异戊烯基转移酶基因。这些基因产物与真菌中的二甲基烯丙基色氨酸合酶具有显著的序列相似性。我们从烟曲霉中克隆并在大肠杆菌和酿酒酵母中过表达了其中六个基因，即fgaPT1、fgaPT2、ftmPT1、ftmPT2、7-dmats和cdpNPT。对过量表达的酶进行了生化特性鉴定。另外分别在曲霉属真菌构巢曲霉和橙色马尔布兰奇霉中鉴定并表征了三种异戊烯基转移酶，即DmaW-Cs、TdiB和MaPT。序列分析、与已知芳香族异戊烯基转移酶的比对以及系统发育分析表明，这些酶属于一组新的“芳香族异戊烯基转移酶”。它们与来自不同来源的膜结合芳香族异戊烯基转移酶和来自细菌的可溶性异戊烯基转移酶明显不同。所表征的酶是可溶性蛋白质，催化各种底物吲哚部分上不同的异戊烯基转移反应，并且其酶促反应不需要二价金属离子。所有这些酶仅接受二甲基烯丙基二磷酸作为异戊烯基供体。另一方面，它们对其芳香族底物表现出广泛的底物特异性。这些酶接受多种色氨酸衍生物和含色氨酸的环二肽，为方便生产生物活性物质提供了一种新策略，例如通过化学酶促合成。
