title: Transiently produced hypochlorite is responsible for the irreversible inhibition of chlorite dismutase.
abstract: Chlorite dismutases (Clds) are heme b-containing prokaryotic oxidoreductases that catalyze the reduction of chlorite to chloride with the concomitant release of molecular oxygen. Over time, they are irreversibly inactivated. To elucidate the mechanism of inactivation and investigate the role of the postulated intermediate hypochlorite, the pentameric chlorite dismutase of "Candidatus Nitrospira defluvii" (NdCld) and two variants (having the conserved distal arginine 173 exchanged with alanine and lysine) were recombinantly produced in Escherichia coli. Exchange of the distal arginine boosts the extent of irreversible inactivation. In the presence of the hypochlorite traps methionine, monochlorodimedone, and 2-[6-(4-aminophenoxy)-3-oxo-3H-xanthen-9-yl]benzoic acid, the extent of chlorite degradation and release of molecular oxygen is significantly increased, whereas heme bleaching and oxidative modifications of the protein are suppressed. Among other modifications, hypochlorite-mediated formation of chlorinated tyrosines is demonstrated by mass spectrometry. The data obtained were analyzed with respect to the proposed reaction mechanism for chlorite degradation and its dependence on pH. We discuss the role of distal Arg173 by keeping hypochlorite in the reaction sphere for O-O bond formation.
authors.affiliation: Department of Chemistry, Division of Biochemistry, VIBT-Vienna Institute of BioTechnology, BOKU-University of Natural Resources and Life Sciences , A-1190 Vienna, Austria.
authors.forename: Stefan
authors.initials: S
authors.lastname: Hofbauer
authors.forename: Clemens
authors.initials: C
authors.lastname: Gruber
authors.forename: Katharina F
authors.initials: KF
authors.lastname: Pirker
authors.forename: Axel
authors.initials: A
authors.lastname: Sündermann
authors.forename: Irene
authors.initials: I
authors.lastname: Schaffner
authors.forename: Christa
authors.initials: C
authors.lastname: Jakopitsch
authors.forename: Chris
authors.initials: C
authors.lastname: Oostenbrink
authors.forename: Paul G
authors.initials: PG
authors.lastname: Furtmüller
authors.forename: Christian
authors.initials: C
authors.lastname: Obinger
mesh_terms: D001419:Bacteria / Q000201:enzymology* / Q000235:genetics; D001426:Bacterial Proteins / Q000037:antagonists & inhibitors / Q000737:chemistry* / Q000235:genetics; D006863:Hydrogen-Ion Concentration; D006997:Hypochlorous Acid / Q000737:chemistry*; D010084:Oxidation-Reduction; D010088:Oxidoreductases / Q000037:antagonists & inhibitors / Q000737:chemistry* / Q000235:genetics; D010100:Oxygen / Q000737:chemistry*; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics
chemical_list: D001426:Bacterial Proteins; D011994:Recombinant Proteins; D006997:Hypochlorous Acid; D010088:Oxidoreductases; C402794:chlorite dismutase; D010100:Oxygen
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