Combinatorial Generation of Complexity by Redox Enzymes in the Chaetoglobosin A Biosynthesis

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• 作者：Kan鈥檌chiro Ishiuchi ; Takehito Nakazawa ; Fumitoshi Yagishita ; Takashi Mino ; Hiroshi Noguchi ; Kinya Hotta ; Kenji Watanabe
• 刊名：The Journal of the American Chemical Society
• 出版年：2013
• 出版时间：May 15, 2013
• 年：2013
• 卷：135
• 期：19
• 页码：7371-7377
• 全文大小：396K
• 年卷期：v.135,no.19(May 15, 2013)
• ISSN：1520-5126

文摘

Redox enzymes play a central role in generating structural complexity during natural product biosynthesis. In the postassembly tailoring steps, redox cascades can transform nascent chemical scaffolds into structurally complex final products. Chaetoglobosin A (1) is biosynthesized by a hybrid polyketide synthase鈥搉onribosomal peptide synthetase. It belongs to the chaetoglobosin family of natural products, comprising many analogs having different degrees of oxidation introduced during their biosynthesis. We report here the determination of the complete biosynthetic steps leading to the formation of 1 from prochaetoglobosin I (2). Each oxidation step was elucidated using Chaetomium globosum strains carrying various combinations of deletion of the three redox enzymes, one FAD-dependent monooxygenase, and two cytochrome P450 oxygenases, and in vivo biotransformation of intermediates by heterologous expression of the three genes in Saccharomyces cerevisiae. Five analogs were identified in this study as intermediates formed during oxidization of 2 to 1 by those redox enzymes. Furthermore, a stereochemical course of each oxidation step was clearly revealed with the absolute configurations of five intermediates determined from X-ray crystal structure. This approach allowed us to quickly determine the biosynthetic intermediates and the enzymes responsible for their formation. Moreover, by addressing the redox enzymes, we were able to discover that promiscuity of the redox enzymes allowed the formation of a network of pathways that results in a combinatorial formation of multiple intermediate compounds during the formation of 1 from 2. Our approach should expedite elucidation of pathways for other natural products biosynthesized by many uncharacterized enzymes of this fungus.