Biosynthesis of HSAF, a Tetramic Acid-Containing Macrolactam from Lysobacter enzymogenes

详细信息    查看全文

• 作者：Lili Lou ; Guoliang Qian ; Yunxuan Xie ; Jiliang Hang ; Haotong Chen ; Kathia Zaleta-Rivera ; Yaoyao Li ; Yuemao Shen ; Patrick H. Dussault ; Fengquan Liu ; Liangcheng Du
• 刊名：Journal of the American Chemical Society
• 出版年：2011
• 出版时间：February 2, 2011
• 年：2011
• 卷：133
• 期：4
• 页码：643-645
• 全文大小：757K
• 年卷期：v.133,no.4(February 2, 2011)
• ISSN：1520-5126

文摘

HSAF was isolated from Lysobacter enzymogenes, a bacterium used in the biological control of fungal diseases of plants. Structurally, it is a tetramic acid-containing macrolactam fused to a tricyclic system. HSAF exhibits a novel mode of action by disrupting sphingolipids important to the polarized growth of filamentous fungi. Here we describe the HSAF biosynthetic gene cluster, which contains only a single-module polyketide synthase/nonribosomal peptide synthetase (PKS/NRPS), although the biosynthesis of HSAF apparently requires two separate polyketide chains that are linked together by one amino acid (ornithine) via two amide bonds. Flanking the PKS/NRPS are six genes that encoding a cascade of four tightly clustered redox enzymes on one side and a sterol desaturase/fatty acid hydroxylase and a ferredoxin reductase on the other side. The genetic data demonstrate that the four redox genes, in addition to the PKS/NRPS gene and the sterol desaturase/fatty acid hydroxylase gene, are required for HSAF production. The biochemical data show that the adenylation domain of the NRPS specifically activates l-ornithine and that the four-domain NRPS is able to catalyze the formation of a tetramic acid-containing product from acyl-S-ACP and ornithinyl-S-NRPS. These results reveal a previously unrecognized biosynthetic mechanism for hybrid PK/NRP in prokaryotic organisms.