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Title:Characterization of a Bromoperoxidase From the Marine Algae Penicillus Capitatus
Author(s):Manthey, John Anthony
Department / Program:Biochemistry
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):Biophysics, General
Abstract:The soluble emzyme bromperoxidase isolated from the marine green algae P. capitatus is capable of catalyzing halide oxiations while in the presence of peroxide. Protein purification and characterization of this enzyme showed that the prosthetic group is ferric protoporphyrin IX and that the enzyme consists of two equal molecular weight subunits whose combined weight is approximately 100,000. Bromoperoxidase contains no detectable level of carbohydrate.
Initial characterization of the oxidized intermediates of bromoperoxidase which result from the protein's reaction with peroxide molecules shows that bromoperoxidase forms typical Compound I and Compound II species. Electron para-magnetic resonance (EPR) measurements failed to show any radical signal associated with Compound I. A third oxidized intermediate, termed Compound III forms as a result of the reaction of peroxide with Compound II or as a reaction product of an oxidase-type reaction involving dihydroxyfumaric acid.
Characterization of the catalytic parameters of bromoperoxidase showed that the enzyme is capable of catalyzing chloride, bromide and iodide ion oxidation. The bromide and iodide oxidation reactions follow similar pH-rate profile equations and have pH optima near ph 6-7. Chloride oxidations follow a second pH-rate profile equation and have pH optima near pH 4. Kinetics of bromide ion oxidation demonstrated that monochlorodimedone (MCD) bromination catalyzed by bromoperoxidase involves tribromide ion formation. The bromide enhanced catalase-type reaction resulting from the catalytic degradation of hydrogen peroxide by bromoperoxidase was also shown to involve tribromide ion formation. Chloride ion oxidation was demonstrated by the isolation of labeled {('36)Cl}-dichlorodimedone synthesized by bromoperoxidase, MCD, peroxide, and Na('36)Cl. Similar chloride enhanced reactions were observed for 2-thiouracil oxidation and the catalase-type reaction. Compound III accumulates during the peroxidative and MCD bromination reactions catalyzed by bromoperoxidase. The accumulation of Compound III greatly affects the reaction rates for the above reactions.
Studies of the ferrous state of bromoperoxidase demonstrated that the enzyme exists as two reduced forms. Similar behavior was observed for the ferrous-carbonmonoxy complexes as well. The ferrous-carbonmonoixy complexes did not show a P-450 type spectrum but rather spectra similar to those observed for peroxidases containing a proximal imidazole ligand. Stepwise reductions of bromoperoxidase showed complicated reduction properties for the enzyme.
Issue Date:1984
Description:212 p.
Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1984.
Other Identifier(s):(UMI)AAI8502234
Date Available in IDEALS:2014-12-15
Date Deposited:1984

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