- Vanadium K-edge XAS studies on the native and peroxo-forms of vanadium chloroperoxidase from Curvularia inaequalis
- Journal of inorganic biochemistry
- Volume | Issue number
- 104 | 6
- Pages (from-to)
- Document type
- Faculty of Science (FNWI)
- Van 't Hoff Institute for Molecular Sciences (HIMS)
Vanadium K-edge X-ray Absorption Spectra have been recorded for the native and peroxo-forms of vanadium chloroperoxidase from Curvularia inaequalis at pH 6.0. The Extended X-ray Absorption Fine Structure (EXAFS) regions provide a refinement of previously reported crystallographic data; one short V = O bond (1.54 Å) is present in both forms. For the native enzyme, the vanadium is coordinated to two other oxygen atoms at 1.69 Å, another oxygen atom at 1.93 Å and the nitrogen of an imidazole group at 2.02 Å. In the peroxo-form, the vanadium is coordinated to two other oxygen atoms at 1.67 Å, another oxygen atom at 1.88 Å and the nitrogen of an imidazole group at 1.93 Å. When combined with the available crystallographic and kinetic data, a likely interpretation of the EXAFS distances is a side-on bound peroxide involving V-O bonds of 1.67 and 1.88 Å; thus, the latter oxygen would be ‘activated’ for transfer. The shorter V-N bond observed in the peroxo-form is in line with the previously reported stronger binding of the cofactor in this form of the enzyme. Reduction of the enzyme with dithionite has a clear influence on the spectrum, showing a change from vanadium(V) to vanadium(IV).
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