Glycolysis nicotinamide adenine dinucleotide

It is well known that the selective transport of ions through a mitochondrial inner membrane is attained when the oxygen supplied by the respiration oxidizes glycolysis products in mitochondria with the aid of such substances as flavin mononucleotide (FMN), fi-nicotinamide adenine dinucleotide (NADH), and quinone (Q) derivatives [1-3]. The energy that enables ion transport has been attributed to that supplied by electron transport through the membrane due to a redox reaction occurring at the aqueous-membrane interface accompanied by respiration [1-5],... 

In the past decade, a large number of studies emphasized the heterogeneous scale-free degree distribution of metabolic networks Most substrates participate in only a few reactions, whereas a small number of metabolites ( hubs ) participate in a very large number of reactions [19,45,52]. Not surprisingly, the list of highly connected metabolites is headed by the ubiquitous cofactors, such as adenosine triphosphate (ATP), adenosine diphosphate (ADP), and nicotinamide adenine dinucleotide (NAD) in its various forms, as well as by intermediates of glycolysis and the tricarboxylic acid (TCA) cycle. 

Figure 6.1 Pathways involved in glucose oxidation by plant cells (a) glycolysis, (b) Krebs cycle, (c) mitochondrial cytochrome chain. Under anoxic conditions. Reactions 1, 2 and 3 of glycolysis are catalysed by lactate dehydrogenase, pyruvate decarboxylase and alcohol dehydrogenase, respectively. ATP and ADP, adenosine tri- and diphosphate NAD and NADHa, oxidized and reduced forms of nicotinamide adenine dinucleotide PGA, phosphoglyceraldehyde PEP, phosphoenolpyruvate Acetyl-CoA, acetyl coenzyme A FP, flavoprotein cyt, cytochrome e, electron. (Modified from Fitter and Hay, 2002). Reprinted with permission from Elsevier...

Both competing reductions consume the cofactor nicotinamide adenine dinucleotide (NADH) and thereby interfere with the redox balance of the cell and feedback on glycolysis where NADH is regenerated on the one hand, while on the other hand NAD+ is required to keep the glycolytic pathway running. The nonlinear dynamical model combines the network of glycolysis and the additional pathways of the xenobiotics to predict the asymmetric yield (enantiomeric excess, ee) of L-versus D-carbinol for different environmental conditions (Fig. 3.4). Here, the enantiomeric excess of fluxes vy and i>d is defined as... 

In the balanced chemical equation for glycolysis, two molecules of NAD+ are converted to two molecules of NADH and two protons. The structure of NAD+ (nicotinamide adenine dinucleotide) is given in Fig. 11.1. This is a reduction reaction, and the NAD+, an enzyme cofactor, has accepted the equivalent of H (a hvdride... 

Niacin is a water-soluble vitamin. The RDA of niacin for the adult man is 19 mg. Niacin is converted in the bi>dy to the cofactor nicotinamide adenine dinucleotide (NAD). NAD also exists in a phosphorylated form, NADP The phosphate group occurs on the 2-hydrr>xyl group of the AMP half of the coenzyme, NAD and NADP are used in the catalysis of oxidation and reduction reactions. These reactions are called redox reactions. NAD cycles between the oxidized form, NAD, and the reduced form, NADH + H. The coenzyme functions to accept and donate electrons. NADP behaves in a similar fashion. It occurs as NADP and NADPH + HT The utilization of NAD is illustrated in the sections on glycolysis, the malatc-aspartate shuttle, ketone body metabolism, and fatty acid oxidation. The utilization of NADP is illustrated in the sectirrns concerning fatty acid synthesis and the pentose phosphate pathway. 

Glycolysis The biochemical process by which glucose is converted to pyruvate in the cytosol of the cell. It results in the production of 2 mol of adenosine triphosphate (ATP) and 2 mol of the reduced cofactor nicotinamide adenine dinucleotide (NADH), which transfers its reducing equivalents to the mitochondrion for the production of ATP via oxidative phosphorylation. 

In the first stage of respiration, a six-carbon glucose molecule is split into a pair of three-carbon molecules. Hydrogen Ions and electrons also are produced in glycolysis. These combine with electron carrier ions called nicotinamide adenine dinucleotide (NAD+) to form NADH. NADH is a coenzyme that is made from vitamin B4, which is also called niacin or nicotinic acid. ATP and NADH serve as temporary storage sites for energy and electrons, respectively, during respiration. Two molecules of ATP are used, and four molecules are produced. ... 

---