Purification and characterisation of vanadium haloperoxidases from the brown alga Pelvetia canaliculata

Two enzymes characterised as iodoperoxidases (PcI and PcII), with vanadium- dependent activity, have been purified from the brown alga Pelvetia canalic ulata (L.) Decne et Thur. (Fucaceae, Phaeophyceae), collected in the Northe rn Portuguese coast, at Viana do Castelo. The relative molecular masses wer e 166 kDa for PcI and 416 kDa for PcII, as determined by gel filtration. SD S-PAGE shows that PcI has just one band corresponding to a subunit of 66 kD a, while PcII shows four bands (66, 72, 157 and 280 kDa). The following kin etic parameters have been determined from a steady-state analysis of the ox idation of iodide by H2O2: PcI, pH(opt) = 6.0, K-M(I-) = 2.1 mM, K-M(H2O2)= 110 mu M, K-i(I-) = 127 mM, and PcII, pH(opt) = 6.5, K-M(I-) = 2.4 mM, K-M (H2O2) = 20 mu M and k(i)(I-) = 69 mM. These iodoperoxidases are thermostab le, as also observed for vanadium bromo- and chloroperoxidases. (C) 2000 El sevier Science ltd. All rights reserved.