Comparison of Nonheme Manganese- and Iron-Containing Flavone Synthase Mimics |
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Authors: | Dra Lakk-Bogth Natalija Pantalon Juraj Bashdar I Meena Berislav Peri Sreko I Kirin Jzsef Kaizer |
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Institution: | 1.Research Group of Bioorganic and Biocoordination Chemistry, University of Pannonia, H-8201 Veszprém, Hungary; (D.L.-B.); (B.I.M.);2.Division of Materials Chemistry, Ruđer Bošković Institute, Bijenička c. 54, HR-10000 Zagreb, Croatia; (N.P.J.); (B.P.); (S.I.K.) |
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Abstract: | Heme and nonheme-type flavone synthase enzymes, FS I and FS II are responsible for the synthesis of flavones, which play an important role in various biological processes, and have a wide range of biomedicinal properties including antitumor, antimalarial, and antioxidant activities. To get more insight into the mechanism of this curious enzyme reaction, nonheme structural and functional models were carried out by the use of mononuclear iron, FeII(CDA-BPA*)]2+ (6) CDA-BPA = N,N,N’,N’-tetrakis-(2-pyridylmethyl)-cyclohexanediamine], FeII(CDA-BQA*)]2+ (5) CDA-BQA = N,N,N’,N’-tetrakis-(2-quinolilmethyl)-cyclohexanediamine], FeII(Bn-TPEN)(CH3CN)]2+ (3) Bn-TPEN = N-benzyl-N,N’,N’-tris(2-pyridylmethyl)-1,2-diaminoethane], FeIV(O)(Bn-TPEN)]2+ (9), and manganese, MnII(N4Py*)(CH3CN)]2+ (2) N4Py* = N,N-bis(2-pyridylmethyl)-1,2-di(2-pyridyl)ethylamine)], MnII(Bn-TPEN)(CH3CN)]2+ (4) complexes as catalysts, where the possible reactive intermediates, high-valent FeIV(O) and MnIV(O) are known and well characterised. The results of the catalytic and stoichiometric reactions showed that the ligand framework and the nature of the metal cofactor significantly influenced the reactivity of the catalyst and its intermediate. Comparing the reactions of FeIV(O)(Bn-TPEN)]2+ (9) and MnIV(O)(Bn-TPEN)]2+ (10) towards flavanone under the same conditions, a 3.5-fold difference in reaction rate was observed in favor of iron, and this value is three orders of magnitude higher than was observed for the previously published FeIV(O)(N2Py2Q*)]2+ N,N-bis(2-quinolylmethyl)-1,2-di(2-pyridyl)ethylamine] species. |
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Keywords: | flavone synthase iron(IV)-oxo manganese(IV)-oxo oxidation kinetic studies |
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