The heme enzyme chlorite dismutase (Cld) catalyzes the degradation of chlorite to chloride and dioxygen. Although structure and steady-state kinetics of Clds have been elucidated, many questions remain (e.g., the mechanism of chlorite cleavage and the pH dependence of the reaction). Here, we present high-resolution X-ray crystal structures of a dimeric Cld at pH 6.5 and 8.5, its fluoride and isothiocyanate complexes and the neutron structure at pH 9.0 together with the pH dependence of the Fe(III)/Fe(II) couple, and the UV− vis and resonance Raman spectral features. We demonstrate that the distal Arg127 cannot act as proton acceptor and is fully ionized even at pH 9.0 ruling out its proposed role in dictating the pH dependence of chlorite degradation. Stopped-flow studies show that (i) Compound I and hypochlorite do not recombine and (ii) Compound II is the immediately formed redox intermediate that dominates during turnover. Homolytic cleavage of chlorite is proposed.

Molecular Mechanism of Enzymatic Chlorite Detoxification: Insights from Structural and Kinetic Studies / Schaffner, Irene; Mlynek, Georg; Flego, Nicola; Pã¼hringer, Dominic; Libiseller-Egger, Julian; Coates, Leighton; Hofbauer, Stefan; Bellei, Marzia; Furtmã¼ller, Paul G.; Battistuzzi, Gianantonio; Smulevich, Giulietta; DjinoviÄ -Carugo, Kristina; Obinger, Christian. - In: ACS CATALYSIS. - ISSN 2155-5435. - STAMPA. - 7:(2017), pp. 7962-7976. [10.1021/acscatal.7b01749]

Molecular Mechanism of Enzymatic Chlorite Detoxification: Insights from Structural and Kinetic Studies

Smulevich, Giulietta;
2017

Abstract

The heme enzyme chlorite dismutase (Cld) catalyzes the degradation of chlorite to chloride and dioxygen. Although structure and steady-state kinetics of Clds have been elucidated, many questions remain (e.g., the mechanism of chlorite cleavage and the pH dependence of the reaction). Here, we present high-resolution X-ray crystal structures of a dimeric Cld at pH 6.5 and 8.5, its fluoride and isothiocyanate complexes and the neutron structure at pH 9.0 together with the pH dependence of the Fe(III)/Fe(II) couple, and the UV− vis and resonance Raman spectral features. We demonstrate that the distal Arg127 cannot act as proton acceptor and is fully ionized even at pH 9.0 ruling out its proposed role in dictating the pH dependence of chlorite degradation. Stopped-flow studies show that (i) Compound I and hypochlorite do not recombine and (ii) Compound II is the immediately formed redox intermediate that dominates during turnover. Homolytic cleavage of chlorite is proposed.
2017
7
7962
7976
Schaffner, Irene; Mlynek, Georg; Flego, Nicola; Pã¼hringer, Dominic; Libiseller-Egger, Julian; Coates, Leighton; Hofbauer, Stefan; Bellei, Marzia; Furtmã¼ller, Paul G.; Battistuzzi, Gianantonio; Smulevich, Giulietta; DjinoviÄ -Carugo, Kristina; Obinger, Christian
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Utilizza questo identificatore per citare o creare un link a questa risorsa: https://hdl.handle.net/2158/1107531
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