Vanadium bromoperoxidase reactivity

Soedjak HS, A Butler (1990) Charactarization of vanadium bromoperoxidase from Macrocystis and Fucus reactivity of bromoperoxidase towards acyl and alkyl peroxides and bromination of amines. Biochemistry 29 7974-7981. 

Carter JN, Beatty KE, Simpson MT, Butler A (2002) Reactivity of Recombinant and Mutant Vanadium Bromoperoxidase from the Red Alga Corallina officinalis. J Inorg Biochem 91 59... 

Alkyl hydroperoxides, including ethyl hydroperoxide, cuminyl hydroperoxide, and tert-butyl hydroperoxide, are not used by V-BrPO to catalyze bromination reactions [29], These alkyl hydroperoxides have the thermodynamic driving force to oxidize bromide however, they are kinetically slow. Several examples of vanadium(V) alkyl peroxide complexes have been well characterized [63], including [V(v)0(OOR)(oxo-2-oxidophenyl) salicylidenaminato] (R = i-Bu, CMe2Ph), which has been used in the selective oxidation of olefins to epoxides. The synthesis of these compounds seems to require elevated temperatures, and their oxidation under catalytic conditions has not been reported. We have found that alkyl hydroperoxides do not coordinate to vanadate in aqueous solution at neutral pH, conditions under which dihydrogen peroxide readily coordinates to vanadate and vanadium( V) complexes (de la Rosa and Butler, unpublished observations). Thus, the lack of bromoperoxidase reactivity with the alkyl hydroperoxides may arise from slow binding of the alkyl hydroperoxides to V-BrPO. 

The haloperoxidases are a class of enzymes that catalyze the oxidation of halides via a reactive peroxometal active site. These enzymes are named according to the most electronegative halide they are able to oxidize. Hence, a bromoperoxidase can oxidize bromide and iodide but not chloride, whereas a chloroperoxidase can oxidize all three. Haloperoxidases are found in most living organisms and predominately fall into two classes the iron heme-based and vanadium-dependent enzymes. Of these, heme-based enzymes are found in mammals, where they provide a vital... 

Figure 5 A possible explanation for the difference in reactivity between vanadium chloroperoxidase and bromoperoxidase ...

A novel class of haloperoxidases, in which a heme prosthetic group was absent, was detected in brown algae (Phaeophyceae) by Vilter and coworkers (13-15). These publications escaped the attention of most biochemists involved in peroxidase research. Only when some of this work was published in the journal Phytochemistry (16) was there as increasing awareness of these findings. A clue for the involvement of vanadium was also published (16). It was shown that the bromoperoxidase could be inactivated at low pH and reactivated by vanadate. These results were subsequently confirmed (17, 18) when it was shown that vanadium was present in a number of bromoperoxidases from different sources and was essential for enzymatic activity. To date, these sources include the enzymes from the brown seaweed Ascophyllum nodosum... 

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