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Molecular mechanism of enzymatic chlorite detoxification: insights from structural and kinetic studies

DOI: 10.1021/acscatal.7b01749 DOI Help

Authors: Irene Schaffner (BOKU – University of Natural Resources and Life Sciences) , Georg Mlynek (University of Vienna) , Nicola Flego (Università di Firenze) , Dominic Puehringer (University of Vienna) , Julian Libiseller-Egger (BOKU – University of Natural Resources and Life Sciences) , Leighton Coates (Oak Ridge National Laboratory) , Stefan Hofbauer (BOKU – University of Natural Resources and Life Sciences) , Marzia Bellei (University of Modena and Reggio Emilia) , Paul G. G. Furtmüller (BOKU – University of Natural Resources and Life Sciences) , Gianantonio Battistuzzi (University of Modena and Reggio Emilia) , Giulietta Smulevich (Università di Firenze) , Kristina Djinovic-Carugo (University of Vienna; University of Ljubljana) , Christian Obinger (BOKU – University of Natural Resources and Life Sciences)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Acs Catalysis

State: Published (Approved)
Published: October 2017
Diamond Proposal Number(s): 16011

Open Access Open Access

Abstract: The heme enzyme chlorite dismutase (Cld) catalyses 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.

Journal Keywords: Chlorite dismutase; heme enzyme; O2 generation; X-ray diffraction; neutron diffraction; stopped-flow spectroscopy; resonance Raman spectroscopy; spectroelectrochemistry

Diamond Keywords: Enzymes

Subject Areas: Chemistry, Biology and Bio-materials


Instruments: I02-Macromolecular Crystallography

Other Facilities: ESRF; ORNL

Added On: 16/10/2017 09:29

Documents:
acs787catal.pdf

Discipline Tags:

Biochemistry Catalysis Chemistry Structural biology Life Sciences & Biotech

Technical Tags:

Diffraction Macromolecular Crystallography (MX)