Reversible, electrochemical interconversion of NADH and NAD+ by the catalytic (Ilambda) subcomplex of mitochondrial NADH:ubiquinone oxidoreductase (complex I).

TitleReversible, electrochemical interconversion of NADH and NAD+ by the catalytic (Ilambda) subcomplex of mitochondrial NADH:ubiquinone oxidoreductase (complex I).
Publication TypeJournal Article
Year of Publication2003
AuthorsZu, Y, Shannon, RJ, Hirst, J
JournalJ Am Chem Soc
Volume125
Issue20
Pagination6020-1
Date Published2003 May 21
ISSN0002-7863
KeywordsElectrochemistry, Electron Transport Complex I, Kinetics, Mitochondria, NAD, NADH, NADPH Oxidoreductases, Oxidation-Reduction
Abstract

NADH:ubiquinone oxidoreductase (complex I) is the first enzyme of the mitochondrial electron transport chain and catalyzes the oxidation of beta-NADH by ubiquinone, coupled to transmembrane proton translocation. It contains a flavin mononucleotide (FMN) at the active site for NADH oxidation, up to eight iron-sulfur (FeS) clusters, and at least one ubiquinone binding site. Little is known about the mechanism of coupled electron-proton transfer in complex I. This communication demonstrates how the catalytic fragment of complex I, subcomplex Ilambda, can be adsorbed onto a pyrolytic graphite edge electrode to catalyze the interconversion of NADH and NAD+, with the electrode as the electron acceptor or donor. NADH oxidation and NAD+ reduction are completely reversible and occur without the application of an overpotential. The potential of zero current denotes the potential of the NAD+/NADH redox couple, and the dependence of ENAD+ on pH, and on the NADH:NAD+ ratio, is in accordance with the Nernst equation. The catalytic potential of the enzyme, Ecat, is close to one of the two reduction potentials of the active site FMN and to the potential of a nearby [2Fe - 2S] cluster; therefore, either one or both of these redox couples is suggested to be important in controlling NADH oxidation by complex I.

DOI10.1021/ja0343961
Alternate JournalJ. Am. Chem. Soc.
Citation Key10.1021/ja0343961
PubMed ID12785808