1-Benzazepine is a pharmaceutically important scaffold but is rare among natural products. Nanangelenin A (1), containing an unprecedented 3,4-dihydro-1-benzazepine-2,5-dione-N-prenyl-N-acetoxy-anthranilamide scaffold, was isolated from a novel species of Australian fungus, Aspergillus nanangensis. Genomic and retrobiosynthetic analyses identified a putative nonribosomal peptide synthetase (NRPS) gene cluster (nan). The detailed biosynthetic pathway to 1 was established by heterologous pathway reconstitution in A. nidulans, which led to biosynthesis of intermediates nanagelenin B-F (2-5 and 7). We demonstrated that the NRPS NanA incorporates anthranilic acid (Ant) and L-kynurenine (L-Kyn), which is supplied by a dedicated indoleamine-2,3-dioxygenase NanC encoded in the gene cluster. Using heterologous in vivo assays and mutagenesis, we demonstrated that the C-terminal condensation (CT) and thiolation (T3) domains of NanA are responsible for the regioselective cyclization of the tethered Ant-L-Kyn dipeptide to form the unusual benzazepine scaffold in 1. We also showed that NanA-CT catalyzes the regioselective cyclization of a surrogate synthetic substrate, Ant-L-Kyn-N-acetylcysteamine, to give the benzazepine scaffold, while spontaneous cyclization of the dipeptide yielded the alternative kinetically favored benzodiazepine scaffold. The discovery of 1 and the characterization of NanA have expanded the chemical and functional diversities of fungal NRPSs.

中文翻译：

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从南南曲霉中生物合成一种新的苯并氮杂生物碱 Nanangelenin A 涉及一种不寻常的 L-犬尿氨酸结合 NRPS 催化区域选择性内酰胺化

1-苯扎西平是一种重要的药学支架，但在天然产物中很少见。Nanangelenin A (1) 含有前所未有的 3,4-dihydro-1-benzazepine-2,5-dione-N-prenyl-N-acetoxy-anthranilamide 支架，是从澳大利亚真菌的一种新物种南南曲霉中分离出来的。基因组和逆生物合成分析确定了一个假定的非核糖体肽合成酶 (NRPS) 基因簇 (nan)。详细的生物合成途径 1 是通过构巢曲霉中的异源途径重建建立的，这导致中间体 nanagelenin BF（2-5 和 7）的生物合成。我们证明了 NRPS NanA 结合了邻氨基苯甲酸 (Ant) 和 L-犬尿氨酸 (L-Kyn)，它由基因簇中编码的专用吲哚胺-2,3-双加氧酶 NanC 提供。使用异源体内试验和诱变，我们证明了 NanA 的 C 端缩合 (CT) 和硫醇化 (T3) 结构域负责连接的 Ant-L-Kyn 二肽的区域选择性环化，以在 1 中形成不寻常的苯并氮杂支架。我们还表明 NanA-CT催化替代合成底物 Ant-L-Kyn-N-乙酰半胱胺的区域选择性环化，得到苯并氮杂支架，而二肽的自发环化产生了另一种动力学有利的苯二氮卓支架。1 的发现和 NanA 的表征扩展了真菌 NRPS 的化学和功能多样性。我们还表明，NanA-CT 催化替代合成底物 Ant-L-Kyn-N-乙酰半胱胺的区域选择性环化，得到苯并氮杂支架，而二肽的自发环化产生了另一种动力学有利的苯二氮卓支架。1 的发现和 NanA 的表征扩展了真菌 NRPS 的化学和功能多样性。我们还表明，NanA-CT 催化替代合成底物 Ant-L-Kyn-N-乙酰半胱胺的区域选择性环化，得到苯并氮杂支架，而二肽的自发环化产生了另一种动力学有利的苯二氮卓支架。1 的发现和 NanA 的表征扩展了真菌 NRPS 的化学和功能多样性。