Abstract
Vanadium-dependent iodoperoxidases from the brown seaweed Saccorhiza polyschides (Lightfoot) Batters, collected at three different locations along the Portuguese west coast, were extracted, purified and characterized. Several extraction procedures were tested, including two-phase aqueous systems. The purification of the iodoperoxidases was achieved using hydrophobic interaction chromatography followed by chromatofocusing. It was possible to isolate three different isoforms of the enzyme, which show mainly iodoperoxidase activity. The three native enzymes have a relative M r around 125 kDa, and two subunits of M r about 64 kDa. Reactivation studies of the apoenzymes with several metal ions revealed that vanadium(V) was essential for enzymatic activity. These enzymes are remarkably thermostable, maintaining their maximum activity up to 50°. The kinetic parameters for the enzyme catalysed iodoperoxidase reaction were obtained at pH 6.1. In the concentration range studied (0.2–8 mM) there was no inhibition by H 2O 2 whereas iodide inhibition was already apparent at the top values of the concentration range studied (2–25 mM).
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