Vanadium haloperoxidases from brown algae of the Laminariaceae family

Vanadium haloperoxidases were extracted, purified and characterized from th ree different species of Laminariaceae - Laminaria saccharina (Linne) Lamou roux, Laminaria hyperborea (Gunner) Foslie and Laminaria ochroleuca de la P ylaie. Two different forms of the vanadium haloperoxidases were purified fr om L. saccharina and L. hyperborea and one form from L, ochroleuca species. Reconstitution experiments in the presence of several metal ions showed th at only vanadium(V) completely restored the enzymes activity. The stability of some enzymes in mixtures of buffer solution and several organic solvent s such as acetone, ethanol, methanol and I-propanol was noteworthy; for ins tance, after 30 days at least 40% of the initial activity for some isoforms remained in mixtures of 3:1 buffer solution/organic solvent. The enzymes w ere also moderately thermostable, keeping full activity up to 40 degreesC. Some preliminary steady-state kinetic studies were performed and apparent M ichaelis-Menten kinetic parameters were determined for the substrates iodid e and hydrogen peroxide. Histochemical studies were also performed in fresh tissue sections from stipe and blade of L. hyperborea and L, saccharina, s howing that haloperoxidase activity was concentrated in the external cortex near the cuticle, although some activity was also observed in the inner co rtical region. (C) 2001 Elsevier Science Ltd. All rights reserved.