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High-resolution XANES studies on vanadium-containing haloperoxidase: pH-dependence and substrate binding
U Küsthardt1, B Hedman, K O Hodgson
1Lehrstuhl für Anorganische Chemie I, TU München, Garching, Germany.
FEBS Letters
|August 23, 1993
Summary
X-ray absorption spectroscopy revealed that hydrogen peroxide interacts with the vanadium site in bromoperoxidase from Ascophyllum nodosum. No significant structural changes were observed across different pH levels or upon bromide addition.
Area of Science:
- Biochemistry
- Biophysical Chemistry
- Marine Biology
Background:
- Vanadium-containing bromoperoxidase (V-BrPO) is an enzyme found in brown algae.
- Understanding the active site structure and substrate interactions is crucial for elucidating enzyme function.
Purpose of the Study:
- To investigate the structural characteristics of the vanadium active site in V-BrPO from Ascophyllum nodosum.
- To determine the effect of pH and substrates (H2O2 and bromide) on the vanadium active site.
Main Methods:
- High-resolution X-ray absorption K-edge spectroscopy (XAS) was employed.
- X-ray absorption near-edge structure (XANES) spectra were recorded at various pH values (4-9) and in the presence of substrates.
Main Results:
- XANES spectra showed well-resolved features, indicating a stable vanadium active site structure across the tested pH range.
- Direct interaction between hydrogen peroxide (H2O2) and the vanadium site was detected.
- No significant energy shift in the XANES spectrum was observed upon addition of bromide.
Conclusions:
- The vanadium active site in Ascophyllum nodosum bromoperoxidase remains structurally consistent across a range of pH values.
- Hydrogen peroxide directly interacts with the vanadium center during the enzymatic process.
- Bromide does not appear to induce immediate structural changes at the vanadium site detectable by XAS.