Vanadium K-edge absorption spectrum of bromoperoxidase from Ascophyllum nodosum
- 12 October 1988
- journal article
- Published by Elsevier BV in Biochimica et Biophysica Acta (BBA) - Protein Structure and Molecular Enzymology
- Vol. 956 (3), 293-299
- https://doi.org/10.1016/0167-4838(88)90146-x
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 ff at least seven oxygen atoms in a distorted octahedral environment with an average bond length of about 2 Å. 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.Keywords
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