Oxidation reactions catalyzed by vanadium chloroperoxidase from Curvulariainaequalis

Vanadium haloperoxidases have been reported to mediate the oxidation of hal ides to hypohalous acid and the sulfoxidation of organic sulfides to the co rresponding sulfoxides in the presence of hydrogen peroxide. However, tradi tional heme peroxidase substrates were reported not to be oxidized by vanad ium haloperoxidases. Surprisingly, we have now found that the recombinant v anadium chloroperoxidase from the fungus Curvularia inaequalis catalyzes th e oxidation of 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS) , a classical chromogenic heme peroxidase substrate. The enzyme mediates th e oxidation of ABTS in the presence of hydrogen peroxide with a turnover fr equency of 11 s(-1) at its pH optimum of 4.0. The K-m of the recombinant en zyme for ABTS was observed to be approximately 35 mu M at this pH value. In addition, the bleaching of an industrial sulfonated azo dye, Chicago Sky B lue 6B, catalyzed by the recombinant vanadium chloroperoxidase in the prese nce of hydrogen peroxide is reported. (C) 2000 Elsevier Science Inc. All ri ghts reserved.