Lactoperoxidase Active Site Structure and Mechanism of Action

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Goff 9304926 The focus of this project is the detailed characterization of bovine lactoperoxidase active site structural and reactivity properties. The enzyme utilizes hydrogen peroxide and thiocyanate ion to generate an oxidized bacteriostatic product. Hence, further characterization of oxidized thiocyanate intermediates will be of importance to a general understanding of peroxidase antimicrobial action. Specific objectives of this project include: (1) definitive assignment of the unusual heme structure of lactoperoxidase; (2) determination of active site structural modifications associated with peroxidase metabolism of thiocarbamide derivatives; (3) full description of lactoperoxidase compound I (doubly oxidized) electronic structure; and (4) identification of a newly discovered lactoperoxidase-mediated SCN- oxidation product. %%% Mammalian heme peroxidase enzymes provide the major non- immunologic protective response to invading microbes. Leukocyte and exocrine fluid peroxidases utilize hydrogen peroxide and halide or pseudohalide ions for oxidative defense against bacteria, parasites, and viruses. The studies proposed will characterize the mechanism by which these peroxidases generate this oxidized bacteriostatic product and to some extent characterize this product. ***