4idf

Structure of the Fragaria x ananassa enone oxidoreductase in complex with NADPH and HMF

spinqualitylabelsall models 4idf, resolution 1.55Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 4idf is a 1 chain structure with sequence from European strawberry. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Ligands: 4XX, EDO, NDP, SO4 Related: 4ida, 4idb, 4idc, 4idd, 4ide Gene: gene28406 (European strawberry) Resources: FirstGlance, OCA, RCSB, PDBsum Publication Abstract from PubMed The last step in the biosynthetic route to the key strawberry flavor compound 4-hydroxy-2,5-dimethyl-3(2H)-furanone (HDMF) is catalyzed by Fragaria x ananassa enone oxidoreductase (FaEO), earlier putatively assigned as quinone oxidoreductase (FaQR). The ripening-induced enzyme catalyzes the reduction of the exocyclic double bond of the highly reactive precursor 4-hydroxy-5-methyl-2-methylene-3(2H)-furanone (HMMF) in a NAD(P)H-dependent manner. To elucidate the molecular mechanism of this peculiar reaction, we determined the crystal structure of FaEO in six different states or complexes at resolutions of </=1.6 A, including those with HDMF as well as three distinct substrate analogs. Our crystallographic analysis revealed a monomeric enzyme whose active site is largely determined by the bound NAD(P)H cofactor, which is embedded in a Rossmann-fold. Considering that the quasi-symmetric enolic reaction product HDMF is prone to extensive tautomerization, whereas its precursor HMMF is chemically labile in aqueous solution, we used the asymmetric and more stable surrogate product 2-ethyl-4-hydroxy-5-methyl-3(2H)-furanone (EHMF) and the corresponding substrate (2E)-ethylidene-4-hydroxy-5-methyl-3(2H)-furanone (EDHMF) to study their enzyme complexes as well. Together with deuterium-labeling experiments of EDHMF reduction by [4R-(2)H]NADH and chiral-phase analysis of the reaction product EHMF, our data show that the 4R-hydride of NAD(P)H is transferred to the unsaturated exocyclic C6 carbon of HMMF, resulting in a cyclic achiral enolate intermediate that subsequently becomes protonated, eventually leading to HDMF. Apart from elucidating this important reaction of the plant secondary metabolism our study provides a foundation for protein engineering of enone oxidoreductases and their application in biocatalytic processes. Structural basis for the enzymatic formation of the key strawberry flavor compound 4-hydroxy-2,5-dimethyl-3(2H)-furanone.,Schiefner A, Sinz Q, Neumaier I, Schwab W, Skerra A J Biol Chem. 2013 Jun 7;288(23):16815-26. doi: 10.1074/jbc.M113.453852. Epub 2013, Apr 15. PMID:23589283 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.

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