title: Vanadium K-edge absorption spectrum of bromoperoxidase from Ascophyllum nodosum.
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.
authors.affiliation: Physikalisches Institut, Universität Bonn, F.R.G.
authors.forename: J
authors.initials: J
authors.lastname: Hormes
authors.forename: U
authors.initials: U
authors.lastname: Kuetgens
authors.forename: R
authors.initials: R
authors.lastname: Chauvistre
authors.forename: W
authors.initials: W
authors.lastname: Schreiber
authors.forename: N
authors.initials: N
authors.lastname: Anders
authors.forename: H
authors.initials: H
authors.lastname: Vilter
authors.forename: D
authors.initials: D
authors.lastname: Rehder
authors.forename: C
authors.initials: C
authors.lastname: Weidemann
mesh_terms: D056890:Eukaryota / Q000201:enzymology*; D010315:Particle Accelerators; D010544:Peroxidases / Q000378:metabolism*; D000459:Phaeophyceae / Q000201:enzymology*; D013057:Spectrum Analysis; D014639:Vanadium; D014965:X-Rays
chemical_list: D014639:Vanadium; D010544:Peroxidases; C026195:bromide peroxidase