title: Disruption of the aspartate to heme ester linkage in human myeloperoxidase: impact on ligand binding, redox chemistry, and interconversion of redox intermediates.
abstract: In human heme peroxidases the prosthetic group is covalently attached to the protein via two ester linkages between conserved glutamate and aspartate residues and modified methyl groups on pyrrole rings A and C. Here, monomeric recombinant myeloperoxidase (MPO) and the variants D94V and D94N were produced in Chinese hamster ovary cell lines. Disruption of the Asp(94) to heme ester bond decreased the one-electron reduction potential E'(0) [Fe(III)/Fe(II)] from 1 to -55 mV at pH 7.0 and 25 degrees C, whereas the kinetics of binding of low spin ligands and of compound I formation was unaffected. By contrast, in both variants rates of compound I reduction by chloride and bromide (but not iodide and thiocyanate) were substantially decreased compared with the wild-type protein. Bimolecular rates of compound II (but not compound I) reduction by ascorbate and tyrosine were slightly diminished in D94V and D94N. The presented biochemical and biophysical data suggest that the Asp(94) to heme linkage is no precondition for the autocatalytic formation of the other two covalent links found in MPO. The findings are discussed with respect to the known active site structure of MPO and its complexes with ligands.
authors: Division of Biochemistry, Department of Chemistry, BOKU-University of Natural Resources and Applied Life Sciences, Muthgasse 18, A-1190 Vienna, Austria.
authors: Martina
authors: M
authors: Zederbauer
authors: Paul G
authors: PG
authors: Furtmüller
authors: Marzia
authors: M
authors: Bellei
authors: Johanna
authors: J
authors: Stampler
authors: Christa
authors: C
authors: Jakopitsch
authors: Gianantonio
authors: G
authors: Battistuzzi
authors: Nicole
authors: N
authors: Moguilevsky
authors: Christian
authors: C
authors: Obinger
mesh_terms: D000818:Animals; D001224:Aspartic Acid / Q000378:metabolism*; D016466:CHO Cells; D006224:Cricetinae; D003412:Cricetulus; D004563:Electrochemistry; D004952:Esters; D006418:Heme / Q000378:metabolism*; D006801:Humans; D007700:Kinetics; D008024:Ligands; D010084:Oxidation-Reduction; D009195:Peroxidase / Q000737:chemistry / Q000378:metabolism*; D011485:Protein Binding; D013057:Spectrum Analysis / Q000379:methods
chemical_list: D004952:Esters; D008024:Ligands; D001224:Aspartic Acid; D006418:Heme; D009195:Peroxidase