• Journal of Microbiology and Biotechnology
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• v.14 no.5
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• pp.914-918
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• 2004

This study was carried out to analyze the metabolic flux of W. kimchii sk10 on pyruvate and ethanol as a carbon source. The sk10 grown on ethanol produced acetate under aerobic conditions rather than under anaerobic conditions. The lactate and acetate were produced on ethanol plus pyruvate by the sk10 grown under aerobic and anaerobic conditions, respectively. The resting cell of sk10 produced 99.1 mM acetate and 17.3 mM lactate under aerobic conditions and 51.1 mM acetate and 62.4 mM lactate under anaerobic conditions from ethanol plus pyruvate, respectively. This result is thought to be due to the difference in the $NADH/NAD^+$ ratio depending on the growth conditions. The 11-fold overproduction of NADH peroxidase results in a low $NADH/NAD^+$ratio under aerobic growth conditions. At the low $NADH/NAD^+$ ratio, the metabolic flux of pyruvate toward lactate has to be shifted to a flux toward acetate without NADH oxidation to $NAD^+$, and ethanol oxidation to acetate coupled to $NAD^+$ reduction to NADH has to be activated.

• Journal of Microbiology and Biotechnology
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• v.14 no.3
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• pp.540-546
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• 2004

We deviced a new graphite-Mn(II) electrode and found that the modified electrode with Mn(II) can catalyze NADH oxidation and $NAD^+$ reduction coupled to electricity production and consumption as oxidizing agent and reducing power, respectively. In fuel cell with graphite-Mn(II) anode and graphite-Fe(III) cathode, the electricity of 1.5 coulomb (A x s) was produced from NADH which was electrochemically reduced by the graphite-Mn(II) electrode. When the initial concentrations of pyruvate and acetaldehyde were adjusted to 40 mM and 200 mM, respectively, about 25 mM lactate and 35 mM ethanol were produced from 40 mM pyruvate and 200 mM acetaldehyde, respectively, by catalysis of ADH and LDH in the electrochemical reactor with $NAD^+$ as cofactor and electricity as reducing power. By using this new electrode with catalytic function, the bioelectrocatalysts are engineered; namely, oxidoreductase (e.g., lactate dehydrogenase) and $NAD^+$ can function for biotransformation without electron mediator and second oxidoreductase for $NAD^+$/NADH recycling.

• Journal of Electrochemical Science and Technology
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• v.2 no.3
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• pp.163-167
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• 2011

Nicotinamide adenine dinucleotide, $NAD^+$, and its reduced form, NADH, play important roles as coenzymes in many enzymatic reactions. Electrochemical methods for $NAD^+$ or NADH detection or generation are drawn attention because it can provide the simple and low cost platform with fairly good sensitivity. In this study, the polysiloxane viologen polymer/diaphorase/hydrophilic polyurethane (PSV/DI/HPU) modified electrodes were simply prepared and demonstrated for bio-electrocatalytic $NAD^+$ sensors. The electrodes were co-immobilized with diaphorase and polysiloxane viologen polymer as an electron mediator followed by the overcoating with HPU membrane. The mixture of the enzyme and the electron mediator was well stabilized within HPU membrane and exhibited good reversibility and stability. The sensitivity was 0.2 $nA{\cdot}{\mu}M^{-1}$ and the detection limit was 28 ${\mu}M$ with a response time of 50 s ($t_{90%}$). The capability for NADH sensor was also observed on the PSV/DI/HPU electrode.

• Nutritional Sciences
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• v.6 no.4
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• pp.189-194
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• 2003

Most of the ethyl alcohol consumed by humans is oxidized to acetaldehyde in the liver by the cytoplasmic alcohol dehydrogenase (ADH) system. For this ADH-catalyzed oxidation of alcohol, $NAD^+$ is required as the coenzyme and $NAD^+$becomes reduced to NADH. As the $NAD^+$becomes depleted and NADH accumulates, alcohol oxidation is reduced. For continued alcohol oxidation, the accumulated NADH must be quickly reoxidized to $NAD^+$, and it is this reoxidation of NADH to $NAD^+$that is known to be the rate-limiting step in the overall oxidation rate of alcohol The reoxidation of NADH to $NAD^+$is catalyzed by lactate dehydrogenase in the cytoplasm of hepatocytes, with pyruvate being utilized as the substrate. The pyruvate may be supplied from alanine as a result of amino acid metabolism via the urea cycle. Also, glutamine is thought to help with the supply of pyruvate indirectly, and to activate the urea cycle by producing $NH_3$. Thus, in the present study, we have examined the effects of alanine and glutamine on the alcohol oxidation rate. We utilized isolated perfused liver tissue in a system where media containing alanine and glutamine was circulated. Our results showed that when alanine (5.0mM) was added to the glucose-free infusion media, the alcohol oxidation rate was increased by 130%. Furthermore, when both glutamine and alanine were added together to the infusion media, the alcohol oxidation rate increased by as much as 190%, and the rate of urea nitrogen production increased by up to 200%. The addition of glutamine (5.0mM) alone to the infusion media did not accelerate the alcohol oxidation rate. The increases in the rates of alcohol oxidation and urea nitrogen production through the addition of alanine and glutamine indicate that these amino acids have contributed to the enhanced supply of pyruvate through the urea cycle. Based on these results, it is concluded that the dietary supplementation of alanine and glutamine could contribute to increased alcohol detoxification through the urea cycle, by enhancing the supply of pyruvate and $NAD^+$to ensure accelerated rates of alcohol oxidation.

• Journal of Microbiology
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• v.43 no.5
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• pp.451-455
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• 2005

In this study, whole cells and a crude enzyme of Candida peltata were applied to an electrochemical bioreactor, in order to induce an increment of the reduction of xylose to xylitol. Neutral red was utilized as an electron mediator in the whole cell reactor, and a graphite-Mn(IV) electrode was used as a catalyst in the enzyme reactor in order to induce the electrochemical reduction of $NAD^+$ to NADH. The efficiency with which xylose was converted to xylitol in the electrochemical bioreactor was five times higher than that in the conventional bioreactor, when whole cells were employed as a biocatalyst. Meanwhile, the xylose to xylitol reduction efficiency in the enzyme reactor using the graphite-Mn (IV) electrode and $NAD^+$ was twice as high as that observed in the conventional bioreactor which utilized NADH as a reducing power. In order to use the graphite-Mn(IV) electrode as a catalyst for the reduction of $NAD^+$ to NADH, a bioelectrocatalyst was engineered, namely, oxidoreductase (e.g. xylose reductase). $NAD^+$ can function in this biotransformation procedure without any electron mediator or a second oxidoreductase for $NAD^+/NADH$ recycling

• Journal of Electrochemical Science and Technology
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• v.5 no.1
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• pp.19-22
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• 2014

Here we report a highly sensitive and stable detection of $NAD^+$ and NADH by the electrode on which diaphorase (DI) is covalently immobilized in viologen polymer network. The network is prepared by the covalent formation of the structure by mixing propylamine viologen (PAV), poly(ethylene glycol)(400) diglycidyl ether (PEGDGE), an diaphorase (DI). The PAV/PEGDGE/DI modified electrode has the sensitivity of $0.02nA{\cdot}{\mu}M$ and the detection limit of $3{\mu}M$ with a response time of 2 s ($t_{90%}$) for NADH sensing.

• BMB Reports
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• v.28 no.6
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• pp.533-537
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• 1995

The detection with lucigenin under physiological conditions is selective for ${\cdot} O_{2}^{-}$, for it can be accepted that lucigenin indicates actual intramembranal $\cdot O_{2}^{-}- formation$. Lucigenin chemiluminescence (CL) was elicited from the plasma membrane (PM) only by addition of reduced pyridine nucleotide. NADPH was preferred to NADH in PM and hepatocytes. This specificity was masked by $NAD(P)^+$ inhibition. The half maximum rate of CL increase was obtained with 1.5 ${\mu}m$ NADH or 55 ${\mu}m$ NADPH in hepatocytes and 6 ${\mu}m$ NADH or 30 ${\mu}m$ NADPH in plasma membranes. Measurement of these NADPH values required the presence of a NADPH-regenerating system. With NADPH the maximal rate obtained was 10 fold higher than with NADH. NADPH and NADH could produce CL when having access from either side of the membrane. They seemed to react with the identical acceptor because NADH-induced CL was also inhibited by $NADP^+$. The characteristics of ${\cdot}O_{2}^{-}-formation$ produced by pyridine nucleotide will be discussed.

• Molecules and Cells
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• v.46 no.8
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• pp.473-475
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• 2023

• Journal of Life Science
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• v.8 no.2
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• pp.203-207
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• 1998

NAD4 as a gene encoding NADH dehydrogenase subunit 4 in the micodhondrion from maize has been cloned using RT-PCR and sequenced for examining RNA edited sites. Analysis of mt cDNA sequences showed the typical RNA editing patterns and unusual base changes as well;RNA editing from cDNA sequences occured base change from c to U in most cases, however transitions from t to g and G to A were also observed. Even though those editings appared to be occurred randomly, RNA edited sites showed mostly in exon 1 and exon 4 regions, when compared with NAD4 cDNA from wheat, locations of edited sites did not consistent with each other suggesting that the phenomenon of RNA editing occured randomly not site-specific manner.

• Rapid Communication in Photoscience
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• v.2 no.2
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• pp.42-45
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• 2013

Natural photosynthesis utilizes solar energy to convert carbon dioxide and water to energy-rich carbohydrates. Substantial use of sunlight to meet world energy demands requires energy storage in useful fuels via chemical bonds because sunlight is intermittent. Artificial photosynthesis research focuses the fundamental natural process to design solar energy conversion systems. Nicotinamide adenine dinucleotide ($NAD^+$) and $NADP^+$ are ubiquitous as electron transporters in biological systems. Enzymatic, chemical, and electrochemical methods have been reported for NADH regeneration. As photochemical systems, visible light-driven catalytic activity of NADH regeneration was carried out using platinum nanoparticles, molecular rhodium and cobalt complexes in the presence of triethanolamine as a sacrificial electron donor. Pt nanoparticles showed photochemical NADH regeneration activity without additional visible light collector molecules, demonstrating that both photoactivating and catalytic activities exist together in Pt nanoparticles. The NADH regeneration of the Pt nanoparticle system was not interfered with the reduction of $O_2$. Molecular cobalt complexes containing dimethylglyoxime ligands also transfer their hydrides to $NAD^+$ with photoactivation of eosin Y in the presence of TEOA. In this photocatalytic reaction, the $NAD^+$ reduction process competed with a proton reduction.