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ABSTRACT: Playing tricks on enzymes: Direct hydroxylation of benzene to phenol was catalyzed by wild-type P450BM3 in the presence of perfluorinated carboxylic acids as decoy molecules. The catalytic turnover rate reached 120 min(-1) per P450. The selectivity towards phenol production was very high and no overoxidation products were detected.
Angewandte Chemie International Edition 05/2013; · 13.45 Impact Factor
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ABSTRACT: Hemoproteins on their metal: We report a novel strategy for the reconstitution of hemoproteins with non-natural metal complexes; simple addition of manganese and ruthenium porphyrin to E. coli cells immediately prior to homogenization yields the reconstituted proteins. We believe that this simple approach could become a standard reconstitution method for hemoproteins.
ChemBioChem 07/2012; 13(14):2045-7. · 3.94 Impact Factor
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ABSTRACT: The stereoselective epoxidation of styrene was catalyzed by H(2) O(2) -dependent cytochrome P450(SPα) in the presence of carboxylic acids as decoy molecules. The stereoselectivity of styrene oxide could be altered by the nature of the decoy molecules. In particular, the chirality at the α-positions of the decoy molecules induced a clear difference in the chirality of the product: (R)-ibuprofen enhanced the formation of (S)-styrene oxide, whereas (S)-ibuprofen preferentially afforded (R)-styrene oxide. The crystal structure of an (R)-ibuprofen-bound cytochrome P450(SPα) (resolution 1.9 Å) revealed that the carboxylate group of (R)-ibuprofen served as an acid-base catalyst to initiate the epoxidation. A docking simulation of the binding of styrene in the active site of the (R)-ibuprofen-bound form suggested that the orientation of the vinyl group of styrene in the active site agreed with the formation of (S)-styrene oxide.
Chemistry - An Asian Journal 06/2012; 7(10):2286-93. · 4.50 Impact Factor
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Angewandte Chemie International Edition 05/2011; 50(23):5315-8. · 13.45 Impact Factor
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ABSTRACT: Vanabins are a unique protein family of vanadium-binding proteins with nine disulfide bonds. Possible binding sites for VO2+ in Vanabin2 from a vanadium-rich ascidian Ascidia sydneiensis samea have been detected by nuclear magnetic resonance study, but the metal selectivity and metal-binding ability of each site was not examined.
In order to reveal functional contribution of each binding site, we prepared several mutants of Vanabin2 by in vitro site-directed mutagenesis and analyzed their metal selectivity and affinity by immobilized metal-ion affinity chromatography and Hummel Dreyer method.
Mutation at K10/R60 (site 1) markedly reduced the affinity for VO2+. Mutation at K24/K38/R41/R42 (site 2) decreased the maximum binding number, but only slightly increased the overall affinity for VO2+. Secondary structure of both mutants was the same as that of the wild type as assessed by circular dichroism spectroscopy. Mutation in disulfide bonds near the site 1 did not affect its high affinity binding capacity, while those near the site 2 decreased the overall affinity for VO2+.
These results suggested that the site 1 is a high affinity binding site for VO2+, while the site 2 composes a moderate affinity site for multiple VO2+.
Biochimica et Biophysica Acta 07/2009; 1790(10):1327-33. · 4.66 Impact Factor
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ABSTRACT: The unusual ascidian ability to accumulate high levels of vanadium ions at concentrations of up to 350 mM, a 10(7)-fold increase over that found in seawater, has been attracting interdisciplinary attention for a century. Accumulated V(V) is finally reduced to V(III) via V(IV) in ascidian vanadocytes. Reducing agents must therefore participate in the reduction. Previously, we identified a vanadium-binding protein, Vanabin2, in which all 18 cysteines form nine disulfide bonds. Here, we report that Vanabin2 is a novel vanadium reductase because partial cleavage of its disulfide bonds results in the reduction of V(V) to V(IV). We propose that Vanabin2 forms a possible electron transfer cascade from the electron donor, NADPH, via glutathione reductase, glutathione, and Vanabin2 to the acceptor, and vanadium ions conjugated through thiol-disulfide exchange reactions.
Biochimica et Biophysica Acta 03/2009; 1794(4):674-9. · 4.66 Impact Factor
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ABSTRACT: Vanadium-binding proteins, or Vanabins, have recently been isolated from the vanadium-rich ascidian, Ascidia sydneiensis samea. Recent reports indicate that Vanabin2 binds twenty V(IV) ions at pH 7.5, and that it has a novel bow-shaped conformation. However, the role of Vanabin2 in vanadium accumulation by the ascidian has not yet been determined. In the present study, the effects of acidic pH on selective metal binding to Vanabin2 and on the secondary structure of Vanabin2 were examined. Vanabin2 selectively bound to V(IV), Fe(III), and Cu(II) ions under acidic conditions. In contrast, Co(II), Ni(II), and Zn(II) ions were bound at pH 6.5 but not at pH 4.5. Changes in pH had no detectable effect on the secondary structure of Vanabin2 under acidic conditions, as determined by circular dichroism spectroscopy, and little variation in the dissociation constant for V(IV) ions was observed in the pH range 4.5-7.5, suggesting that the binding state of the ligands is not affected by acidification. Taken together, these results suggest that the reason for metal ion dissociation upon acidification is attributable not to a change in secondary structure but, rather, that it is caused by protonation of the amino acid ligands that complex with V(IV) ions.
Biochimica et Biophysica Acta 08/2006; 1760(7):1096-101. · 4.66 Impact Factor
