7enb
iron and alpha-ketoglutarate-dependent endoperoxidase NvfI with different conformation
Structural highlights
FunctionNVFI_ASPN1 Fe(II)/2-oxoglutarate-dependent dioxygenase; part of the gene cluster that mediates the biosynthesis of novofumigatonin, a heavily oxygenated meroterpenoid containing a unique orthoester moiety (PubMed:29968715). The first step of the pathway is the synthesis of 3,5-dimethylorsellinic acid (DMOA) by the polyketide synthase nvfA via condensation of one acetyl-CoA starter unit with 3 malonyl-CoA units and 2 methylations (PubMed:29968715). DMOA is then converted to farnesyl-DMOA by the farnesyltransferase nvfB (PubMed:29968715). Epoxydation by FAD-dependent monooxygenase nvfK, followed by a protonation-initiated cyclization catalyzed by the terpene cyclase nvfL leads to the production of asnavolin H (PubMed:29968715). The short chain dehydrogenase nvfC then as a 3-OH dehydrogenase of asnovolin H to yield chemesin D (PubMed:29968715). There are two branches to synthesize asnovolin A from chemesin D (PubMed:29968715). In one branch, chemesin D undergoes Baeyer-Villiger oxidation by nvfH, methylation by nvfJ, and enoyl reduction by the nvfM D enoylreductase that reduces the double bond between C-5'and C-6', to form respectively asnovolin I, asnovolin K, and asnovolin A (PubMed:29968715). In the other branch, the methylation precedes the Baeyer-Villiger oxidation and the enoyl reduction to yield asnovolin A via the asnovolin J intermediate (PubMed:29968715). Asnovolin A is further converted to fumigatonoid A by the Fe(II)/2-oxoglutarate-dependent dioxygenase nvfI that catalyzes an endoperoxidation reaction (PubMed:29968715). The alpha/beta hydrolase nvfD then acts as an epimerase that converts fumigatonoid A to its C-5' epimer, which then undergoes spontaneous or nvfD-catalyzed lactonization (PubMed:29968715). The following step utilizes the ketoreductase nvfG to produce fumigatonoid B (PubMed:29968715). The dioxygenase nvfE further converts fumigatonoid B into fumigatonoid C (PubMed:29968715). Finally the Fe(II)/2-oxoglutarate-dependent dioxygenase nvfF catalyzes two rounds of oxidation to transform fumigatonoid C into the end product, novofumigatonin A (PubMed:29968715).[1] Publication Abstract from PubMedEndoperoxide-containing natural products are a group of compounds with structurally unique cyclized peroxide moieties. Although numerous endoperoxide-containing compounds have been isolated, the biosynthesis of the endoperoxides remains unclear. NvfI from Aspergillus novofumigatus IBT 16806 is an endoperoxidase that catalyzes the formation of fumigatonoid A in the biosynthesis of novofumigatonin. Here, we describe our structural and functional analyses of NvfI. The structural elucidation and mutagenesis studies indicate that NvfI does not utilize a tyrosyl radical in the reaction, in contrast to other characterized endoperoxidases. Further, the crystallographic analysis reveals significant conformational changes of two loops upon substrate binding, which suggests a dynamic movement of active site during the catalytic cycle. As a result, NvfI installs three oxygen atoms onto a substrate in a single enzyme turnover. Based on these results, we propose a mechanism for the NvfI-catalyzed, unique endoperoxide formation reaction to produce fumigatonoid A. Molecular insights into the endoperoxide formation by Fe(II)/alpha-KG-dependent oxygenase NvfI.,Mori T, Zhai R, Ushimaru R, Matsuda Y, Abe I Nat Commun. 2021 Jul 20;12(1):4417. doi: 10.1038/s41467-021-24685-6. PMID:34285212[2] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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