Bromoperoxidase activity of amavadin dissected: a DFT investigation

Bromoperoxidase catalytic activity exerted by oxidated amavadin [V(HIDPA)2](-) (HIDPA = 2,2'-(hydroxyimino) dipropionate) in mono- and bis-protonated forms has been investigated by DFT. Possible reaction pathways for formation of peroxido/hydroperoxido complexes and subsequent bromide oxidation have been systematically dissected. The effect of increasing [H(+)] on catalytically active species and on halogenide oxidation has been also studied. Similarly to vanadium haloperoxidase (VHPO), the results point to a hydroperoxido amavadin adduct as the most reactive species toward bromide oxidation. However, comparison of the reactivity of amavadin and VHPO reveals also crucial differences in the catalytic mechanism of such natural V complexes.