Reactivity of Vanadium Bromoperoxidase

Abstract

Vanadium haloperoxidases catalyze the halogenation of organic substrates (i.e., chloride, bromide or iodide) or the halide-assisted (i.e., chloride, bromide or iodide) disproportionation of hydrogen peroxide forming dioxygen and water. Competitive kinetic studies and fluorescent quenching studies have been used to probe binding of organic substrates to vanadium bromoperoxidase (V-BrPO). Certain organic substrates have been found to bind to V-BrPO such as the indole derivatives presented herein, among other substrates. When organic substrates bind to V-BrPO, a freely diffusible oxidized bromine intermediate is not released from the enzyme active site. The pH dependence and the selectivity of V-BrPO is also examined.