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