Publication Type Journal Article
Title Proton-coupled electron transfer mechanisms of the copper centres of nitrous oxide reductase from Marinobacter hydrocarbonoclasticus - An electrochemical study
Authors Cintia Carreira Margarida Correia dos Santos S. R. Pauleta Isabel Moura
Groups CE
Year 2020
Month June
Volume 133
Abstract Reduction of N2O to N-2 is catalysed by nitrous oxide reductase in the last step of the denitrification pathway. This multicopper enzyme has an electron transferring centre, CuA, and a tetranuclear copper-sulfide catalytic centre, CuZ , which exists as CuZ*(4Cu1S) or CuZ(4Cu2S). The redox behaviour of these metal centres in Marinobacter hydrocarbonoclasticus nitrous oxide reductase was investigated by potentiometry and for the first time by direct electrochemistry. The reduction potential of CuA and CuZ(4Cu2S) was estimated by potentiometry to be +275 +/- 5 mV and +65 +/- 5 mV vs SHE, respectively, at pH 7.6. A proton-coupled electron transfer mechanism governs CuZ(4Cu2S) reduction potential, due to the protonation/deprotonation of Lys397 with a pK(ox) of 6.0 +/- 0.1 and a pK(red) of 9.2 +/- 0.1. The reduction potential of CuA, in enzyme samples with CuZ*(4Cu1S), is controlled by protonation of the coordinating histidine residues in a two-proton coupled electron transfer process. In the cyclic voltammograms, two redox pairs were identified corresponding to CuA and CuZ(4Cu2S), with no additional signals being detected that could be attributed to CuZ*(4Cu1S). However, an enhanced cathodic signal for the activated enzyme was observed under turnover conditions, which is explained by the binding of nitrous oxide to CuZ(0)(4Cu1S), an intermediate species in the catalytic cycle. (C) 2020 Elsevier B.V. All rights reserved.
Book Title
ISSN 1567-5394
EISSN 1878-562X
Conference Name
Bibtex ID ISI:000531827700010
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