Resolving complexity in the interactions of redox enzymes and their inhibitors: contrasting mechanisms for the inhibition of a cytochrome c nitrite reductase revealed by protein pilm voltammetry

Gwyer, James D., Richardson, David J. ORCID: https://orcid.org/0000-0002-6847-1832 and Butt, Julea N. ORCID: https://orcid.org/0000-0002-9624-5226 (2005) Resolving complexity in the interactions of redox enzymes and their inhibitors: contrasting mechanisms for the inhibition of a cytochrome c nitrite reductase revealed by protein pilm voltammetry. Biochemistry, 43 (47). pp. 15086-15094.

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Abstract

Cytochrome c nitrite reductase is a dimeric decaheme-containing enzyme that catalyzes the reduction of nitrite to ammonium. The contrasting effects of two inhibitors on the activity of this enzyme have been revealed, and defined, by protein film voltammetry (PFV). Azide inhibition is rapid and reversible. Variation of the catalytic current magnitude describes mixed inhibition in which azide binds to the Michaelis complex ( 40 mM) with a lower affinity than to the enzyme alone ( 15 mM) and leads to complete inhibition of enzyme activity. The position of the catalytic wave reports tighter binding of azide when the active site is oxidized ( 39 µM) than when it is reduced. By contrast, binding and release of cyanide are sluggish. The higher affinity of cyanide for reduced versus oxidized forms of nitrite reductase is immediately revealed, as is the presence of two sites for cyanide binding and inhibition of the enzyme. Formation of the monocyano complex by reduction of the enzyme followed by a “rapid” scan to high potentials captures the activity-potential profile of this enzyme form and shows it to be distinct from that of the uninhibited enzyme. The biscyano complex is inactive. These studies demonstrate the complexity that can be associated with inhibitor binding to redox enzymes and illustrate how PFV readily captures and deconvolves this complexity through its impact on the catalytic properties of the enzyme.

Item Type:	Article
Faculty \ School:	Faculty of Science > School of Biological Sciences
UEA Research Groups:	Faculty of Science > Research Groups > Organisms and the Environment Faculty of Science > Research Groups > Molecular Microbiology Faculty of Science > Research Centres > Centre for Molecular and Structural Biochemistry Faculty of Science > Research Groups > Energy Materials Laboratory Faculty of Science > Research Groups > Chemistry of Light and Energy Faculty of Science > Research Groups > Chemistry of Life Processes Faculty of Science > Research Groups > Biophysical Chemistry (former - to 2017)
Depositing User:	Rachel Smith
Date Deposited:	17 Feb 2011 12:23
Last Modified:	16 May 2023 23:56
URI:	https://ueaeprints.uea.ac.uk/id/eprint/21413
DOI:	10.1021/bi049085x

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