Metalloenzyme Catalyzed Halogenations

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The goal of this award is to elucidate the reactivities and mechanisms of two newly discovered haloperoxidase metalloenzymes, a vanadium bromoperoxidase (V-BrPO) and a non-heme iron (III) bromoperoxidase (FeNH-BrPO) which are both isolated from marine algae. V-BrPO and FeNH-BrPO are the first non-heme haloperoxidases to be discovered. Experiments are planned to test whether each metal ion functions as a Lewis acid catalyst or as an electron transfer catalyst, shuttling between different oxidation states. Both V-BrPO and FeNH-BrPO catalyze the bromination of pyrimidine- containing nucleic acids, cytosine and uracil. The reactivities of the two enzymes will be studied in terms of a) the types of organic compounds that can be brominated, b) the catalase and superoxide dismutase activity of the enzymes and c) the mechanism of reoxidation of the reduced derivatives of the enzymes. Halogenated organic compounds occur widely in marine organisms. Some of them have exciting biological activity. They represent a valuable, but neglected natural resource. The proposed research will help us understand how the myriad halogenated compounds are formed.