Lauterbach 2013 FEBS J

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Lauterbach L, Lenz O, Vincent KA (2013) Hβ‚‚-driven cofactor regeneration with NAD(P)⁺-reducing hydrogenases. FEBS J 280:3058-68.

Β» PMID: 23497170 Open Access

Lauterbach L, Lenz O, Vincent KA (2013) FEBS J

Abstract: A large number of industrially relevant enzymes depend upon nicotinamide cofactors, which are too expensive to be added in stoichiometric amounts. Existing NAD(P)H-recycling systems suffer from low activity, or the generation of side products. Hβ‚‚-driven cofactor regeneration has the advantage of 100% atom efficiency and the use of Hβ‚‚ as a cheap reducing agent, in a world where sustainable energy carriers are increasingly attractive. The state of development of Hβ‚‚-driven cofactor-recycling systems and examples of their integration with enzyme reactions are summarized in this article. The Oβ‚‚-tolerant NAD⁺-reducing hydrogenase from Ralstonia eutropha is a particularly attractive candidate for this approach, and we therefore discuss its catalytic properties that are relevant for technical applications.

β€’ Bioblast editor: Gnaiger E

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Hydrogen ion ambiguities in the electron transfer system

Communicated by Gnaiger E (2023-10-08) last update 2023-11-10
Electron (e-) transfer linked to hydrogen ion (hydron; H+) transfer is a fundamental concept in the field of bioenergetics, critical for understanding redox-coupled energy transformations.
Ambiguity alert H+.png
However, the current literature contains inconsistencies regarding H+ formation on the negative side of bioenergetic membranes, such as the matrix side of the mitochondrial inner membrane, when NADH is oxidized during oxidative phosphorylation (OXPHOS). Ambiguities arise when examining the oxidation of NADH by respiratory Complex I or succinate by Complex II.
Ambiguity alert e-.png
Oxidation of NADH or succinate involves a two-electron transfer of 2{H++e-} to FMN or FAD, respectively. Figures indicating a single electron e- transferred from NADH or succinate lack accuracy.
Ambiguity alert NAD.png
The oxidized NAD+ is distinguished from NAD indicating nicotinamide adenine dinucleotide independent of oxidation state.
NADH + H+ β†’ NAD+ +2{H++e-} is the oxidation half-reaction in this H+-linked electron transfer represented as 2{H++e-} (Gnaiger 2023). Putative H+ formation shown as NADH β†’ NAD+ + H+ conflicts with chemiosmotic coupling stoichiometries between H+ translocation across the coupling membrane and electron transfer to oxygen. Ensuring clarity in this complex field is imperative to tackle the apparent ambiguity crisis and prevent confusion, particularly in light of the increasing number of interdisciplinary publications on bioenergetics concerning diagnostic and clinical applications of OXPHOS analysis.
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