58-68-4Relevant articles and documents
Mechanistic Aspects of the Electrochemical Oxidation of Dihydronicotinamide Adenine Dinucleotide (NADH)
Moiroux, Jacques,Elving, Philip J.
, p. 6533 - 6538 (1980)
The apparently single stage anodic oxidation of NADH involving removal of two electrons and a proton to form NAD+ has been examined with particular attention to the deprotonation step and its relationship to the initial potential-determining electron-transfer step, primarily at glassy carbon electrodes (GCE) in aqueous media with supplementary studies at pyrolytic graphite and platinum electrodes in aqueous media and at GCE in Me2SO; the carbon electrodes were generally first covered with an adsorbed NAD+ layer in order to eliminate adsorption-controlled faradaic processes.The initial step is an irreversible heterogeneous electron transfer (transfer coefficient β = 0.37 at carbon electrodes and 0.43 at platinum).The resulting cation radical NAD.H+ loses a proton (first-order reaction; rate constant k) to form the neutral radical NAD. which may participate in a second heterogeneous electron transfer (ECE mechanism) or in a homogeneous electron transfer with NAD.H+ (disproportionation mechanism DISP 1 or half-regeneration mechanism), yielding NAD+.The near identities of current functions, viscosity-corrected diffusion coefficients D and β values, point to essentially similar solute species and charge-transfer paths being involved in different media and at different electrodes.D is ca. 2 x 10-6 cm2 s-1 in aqueous solution; k is ca. 60 s-1 at the GCE covered with adsorbed NAD+.
Design of artificial metalloenzymes for the reduction of nicotinamide cofactors
Basle, Mattias,Padley, Henry A.W.,Martins, Floriane L.,Winkler, Gerlof Sebastiaan,J?ger, Christof M.,Pordea, Anca
, (2021/04/19)
Artificial metalloenzymes result from the insertion of a catalytically active metal complex into a biological scaffold, generally a protein devoid of other catalytic functionalities. As such, their design requires efforts to engineer substrate binding, in addition to accommodating the artificial catalyst. Here we constructed and characterised artificial metalloenzymes using alcohol dehydrogenase as starting point, an enzyme which has both a cofactor and a substrate binding pocket. A docking approach was used to determine suitable positions for catalyst anchoring to single cysteine mutants, leading to an artificial metalloenzyme capable to reduce both natural cofactors and the hydrophobic 1-benzylnicotinamide mimic. Kinetic studies revealed that the new construct displayed a Michaelis-Menten behaviour with the native nicotinamide cofactors, which were suggested by docking to bind at a surface exposed site, different compared to their native binding position. On the other hand, the kinetic and docking data suggested that a typical enzyme behaviour was not observed with the hydrophobic 1-benzylnicotinamide mimic, with which binding events were plausible both inside and outside the protein. This work demonstrates an extended substrate scope of the artificial metalloenzymes and provides information about the binding sites of the nicotinamide substrates, which can be exploited to further engineer artificial metalloenzymes for cofactor regeneration. Synopsis about graphical abstract: The manuscript provides information on the design of artificial metalloenzymes based on the bioconjugation of rhodium complexes to alcohol dehydrogenase, to improve their ability to reduce hydrophobic substrates. The graphical abstract presents different binding modes and results observed with native cofactors as substrates, compared to the hydrophobic benzylnicotinamide.
Chemo-bio catalysis using carbon supports: application in H2-driven cofactor recycling
Cleary, Sarah E.,Grobert, Nicole,Reeve, Holly A.,Vincent, Kylie A.,Zhao, Xu,Zor, Ceren
, p. 8105 - 8114 (2021/06/22)
Heterogeneous biocatalytic hydrogenation is an attractive strategy for clean, enantioselective CX reduction. This approach relies on enzymes powered by H2-driven NADH recycling. Commercially available carbon-supported metal (metal/C) catalysts are investigated here for direct H2-driven NAD+reduction. Selected metal/C catalysts are then used for H2oxidation with electrons transferredviathe conductive carbon support material to an adsorbed enzyme for NAD+reduction. These chemo-bio catalysts show improved activity and selectivity for generating bioactive NADH under ambient reaction conditions compared to metal/C catalysts. The metal/C catalysts and carbon support materials (all activated carbon or carbon black) are characterised to probe which properties potentially influence catalyst activity. The optimised chemo-bio catalysts are then used to supply NADH to an alcohol dehydrogenase for enantioselective (>99% ee) ketone reductions, leading to high cofactor turnover numbers and Pd and NAD+reductase activities of 441 h?1and 2347 h?1, respectively. This method demonstrates a new way of combining chemo- and biocatalysis on carbon supports, highlighted here for selective hydrogenation reactions.
