How covalent heme to protein bonds influence the formation and reactivity of redox intermediates of a bacterial peroxidase [Protein Structure and Folding]

September 22nd, 2014 by Auer, M., Nicolussi, A., Schuetz, G., Furtmueller, P. G., Obinger, C.

The most striking feature of mammalian peroxidases including myeloperoxidase (MPO) and lactoperoxidase (LPO) is the existence of covalent bonds between the prosthetic group and the protein, which has a strong impact on their (electronic) structure and biophysical and chemical properties. Recently, a novel bacterial heme peroxidase with high structural and functional similarities to LPO was described. Being released from E. coli, it contains mainly heme b, which can be autocatalytically modified and covalently bound to the protein by incubation with hydrogen peroxide. In the present study, we investigated the reactivity of these two forms in their ferric, Compound I and Compound II state in a multi mixing stopped flow study. Upon heme modification, the reactions between the ferric proteins with cyanide or H2O2 were accelerated. Moreover, apparent bimolecular rate constants of the reaction of Compound I with iodide, thiocyanate, bromide and tyrosine increased significantly and became similar to LPO. Kinetic data are discussed and compared to known structure function relationships of the mammalian peroxidases LPO and MPO.
  • Posted in Journal of Biological Chemistry, Publications
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