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  • Title: Vanadium K-edge absorption spectrum of bromoperoxidase from Ascophyllum nodosum.
    Author: Hormes J, Kuetgens U, Chauvistre R, Schreiber W, Anders N, Vilter H, Rehder D, Weidemann C.
    Journal: Biochim Biophys Acta; 1988 Oct 12; 956(3):293-9. PubMed ID: 3167074.
    Abstract:
    With synchrotron radiation from the Bonn 2.5 GeV synchrotron, high-resolution absorption spectra have been measured at the vanadium K-edge of bromoperoxidase from the marine brown alga Ascophyllum nodosum and several model compounds. The near-edge structure (XANES) of these spectra was used to determine the charge state and the coordination geometry around the vanadium atom. For the active enzyme a coordination charge of 2.7 was found which is compatible with a formal valence of +5, assuming coordination by atoms with a high electronegativity such as oxygen or nitrogen. For the reduced enzyme the coordination charge value of 2.15 indicates the reduction of the valency by 1 unit. Our results suggest that the coordination sphere of the vanadium atom in the native enzyme consists of at least seven oxygen atoms in a distorted octahedral environment with an average bond length of about 2 A. Through the reduction process, the coordination sphere of the vanadium atom changes with a simultaneous decrease of the coordination cage. These results agree with those deduced from previous EPR and 51V-NMR measurements.
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