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[摘要]:Saframycin A is a potent antitumor antibiotic with a unique pentacyclic tetrahydroisoquinoline scaffold. We found that the nonribosomal peptide synthetase SfmC catalyzes a seven-step transformation of readily synthesized dipeptidyl substrates with long acyl chains into a complex saframycin scaffold. Based on a series of enzymatic reactions, we propose a detailed mechanism involving the reduction of various peptidyl thioesters by a single R domain followed by iterative C domain-mediated Pictet-Spengler reactions. |
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