A biomimetic model of vanadium-containing bromoperoxidase (BPO) was proposed. The vanadium-containing BPO possesses vanadate ion (+5 oxidation state) as a prosteric group and catalyses the formation of a carbon-bromide bond in the presence of hydrogen peroxide, bromide ion and bromide acceptor. The reaction mechanism is as yet unknown. Several vanadyl (VO2+, +4 oxidation state) complexes with oxalate, glutarate, succinate, malonate and acetate ligands showed similar bromination activity to that of BPO. Especially, the vanadyl-oxalato complex provided the highest BPO-like activity. Both vanadate ion and vanadyl complexes with nitrogen-containing ligands such as EDTA, glycine and serine showed essentially no BPO-like activity. Thus, the vanadyl-oxalato complex is proposed to be not only a possible chemical model of BPO, but a useful compound to elucidate the reaction mechanism of BPO.
