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  • Title: Time-dependent density functional theory-assisted absolute configuration determination of cis-dihydrodiol metabolite produced from isoflavone by biphenyl dioxygenase.
    Author: Seo J, Kang SI, Kim M, Won D, Takahashi H, Ahn JH, Chong Y, Lee E, Lim Y, Kanaly RA, Han J, Hur HG.
    Journal: Anal Biochem; 2010 Feb 01; 397(1):29-36. PubMed ID: 19854147.
    Abstract:
    Escherichia coli cells containing the biphenyl dioxygenase genes bphA1A2A3A4 from Pseudomonas pseudoalcaligenes KF707 were found to biotransform isoflavone and produced a metabolite that was not found in a control experiment. Liquid chromatography/mass spectrometry (LC/MS) and (1)H and (13)C nuclear magnetic resonance (NMR) analyses indicated that biphenyl dioxygenase induced 2',3'-cis-dihydroxylation of the B-ring of isoflavone. In a previous report, the same enzyme showed dioxygenase activity toward flavone, producing flavone 2',3'-cis-dihydrodiol. Due to growing interest in flavone chemistry and the absolute configuration of natural products, time-dependent density functional theory (TD-DFT) calculations were combined with circular dichroism (CD) spectroscopy to determine the absolute configuration of the isoflavone dihydrodiol. By computational methods, the structure of the isoflavone metabolite was determined to be 3-[(5S,6R)-5,6-dihydroxycyclohexa-1,3-dienyl]-4H-chromen-4-one. This structure was confirmed further by the modified Mosher's method. The same protocol was applied to the flavone metabolite, and the absolute configuration was determined to be 2-[(5S,6R)-5,6-dihydroxycyclohexa-1,3-dienyl]-4H-chromen-4-one. After determination of the absolute configurations of the biotransformation products, we suggest the binding mode of these substrate analogs to the enzyme active site.
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