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Enzyme Kinetics and Drugs as Enzyme Inhibitors
Published in Peter Grunwald, Pharmaceutical Biocatalysis, 2019
The polyol pathway enzyme aldose reductase (for an overview on docking studies with aldose reductase inhibitors see Zeyad et al., 2016) is implicated in diabetic complications. In the case of hyperglycemia glucose becomes reduced by aldose reductase at the expense of NADPH to sorbitol that subsequently is converted to fructose in presence of NAD+. The resulting shortage of NADPH and NAD+ leads among others to diminished glutathione levels associated with enhanced occurrence of oxidative stress and inflammatory processes, e.g., in eyes (retinopathy), heart (cardiovascular disease), kidney (nephropathy), and nerves and feet (neuropathy). The tripeptide glutathione (cysteine, glutamic acid, and glycine) is present in most mammalian tissue and acts as an antioxidant, a free radical scavenger and a detoxifying agent. The relation between cancer as well as other chronic diseases and oxidative stress relies on the fact that oxidative stress activates transcription factors (NF-κB, AP-1, p53, HIF-1α, PPAR-γ, β-catenin/Wnt, Nrf2, MAFK, etc.) leading to the expression of several hundred genes encoding growth factors, inflammatory cytokines, chemokines, cell cycle regulatory molecules, and anti-inflammatory molecules (Reuter et al., 2010; Sosa et al., 2013; Okita et al., 2017).
Outdoor Air Pollution
Published in William J. Rea, Kalpana D. Patel, Reversibility of Chronic Disease and Hypersensitivity, Volume 4, 2017
William J. Rea, Kalpana D. Patel
Cycling cells have higher NADPH/NADP+ ratios than postmitotic cells.242 Cultured cells must double their biomass each day in preparation for division. Postmitotic cells in tissues do not increase in their biomass. Postmitotic cells direct electrons to NADH for cellular work, not NADPH for biomass production. This essential difference between growing and nongrowing cells must be grasped before the different roles of mitochondria in growing and nongrowing cells can be understood. The synthesis of lipids, proteins, DNA, and RNA requires the use of electrons carried by NADPH to make new carbon–carbon and other chemical bonds. NADPH is made in large amounts by the pentose phosphate pathway in which glucose 6-phosphate is used before entering glycolysis to make ribose for DNA and RNA synthesis and NADPH for macromolecular synthesis and glutathione metabolism.243 When incoming electrons from glucose and other nutrients are directed to NADPH, those electrons are not available for NADH used in mitochondrial oxidative phosphorylation. The combined effect of increased NADPH and hyperoxia (21% O2) in cell culture conspires to amplify superoxide and hydrogen peroxide production by NADPH oxidases, making the study of more subtle factors such as regulation of the pentose phosphate pathway by nitric oxide244 and compartmental redox regulation during differentiation challenging or impossible.
Multiphoton imaging of the retina
Published in Pablo Artal, Handbook of Visual Optics, 2017
Robin Sharma, Jennifer J. Hunter
Coenzymes such as NAD(P)H and flavoproteins like FAD are crucial for mitochondria-based cellular respiration pathways such as oxidative phosphorylation. Many retinal layers are densely packed with mitochondria because the retina is more metabolically active than the brain per unit weight (Wong-Riley, 2010). These molecules are of critical importance for cell survival and play the following roles during cellular respiration: NADH and NADPH are the reduced forms of the coenzymes nicotinamide adenine dinucleotide (NAD+) and nicotinamide adenine dinucleotide phosphate (NADP+), respectively, and serve as reducing agents. NADH, a key component of cellular respiration, is generated in the cytoplasm during glycolysis. It is also produced in the mitochondria by the Krebs cycle (also known as the citric acid cycle) during aerobic respiration. NADH donates electrons in complex I, the first stage of the electron transport chain (oxidative phosphorylation), which generates adenosine triphosphate (ATP), a unit of intracellular energy. Thus, glycolysis and the Krebs cycle produce NADH, while the electron transport chain consumes NADH.Flavin adenine dinucleotide (FAD) is also strongly fluorescent. FAD moves electrons between the Krebs cycle and complex II, the second stage of the electron transport chain. FAD is used during the Krebs cycle and produced during the electron transport chain.
Enhancement of erythritol production by Trichosporonoides oedocephalis ATCC 16958 through regulating key enzyme activity and the NADPH/NADP ratio with metal ion supplementation
Published in Preparative Biochemistry and Biotechnology, 2018
Liangzhi Li, Pei Kang, Xin Ju, Jiajia Chen, Huibin Zou, Cuiying Hu, Lishi Yan
Finally, the pentose phosphate pathway is a major way to produce NADPH for reductive biosynthesis reactions.[32] In general, NADPH/NADP ratio >1.0, glucose-6-phosphate dehydrogenase (G6PD), and 6-Phosphogluconate dehydrogenase (6PGD) are responsible for most of NADPH production in the cytosol.[33] Specifically, NAD(P)H is essential for erythritol and glycerol synthesis as a cofactor.[5] Since T. oedocephalis consumes NADPH during the catalytic conversion of glucose to erythritol and redox potential is largely dependent on the balance between NADPH/NADP and NAD/NADH in cells, we further measured the intracellular ratio of NADPH/NADP. As shown in Figure 4, the NADPH/NADP ratio was slightly lower in T. oedocephalis cells cultured with Cu2+ in fermentation medium, compared with that of control cells. Therefore, total production of polyols (data not shown), which includes erythritol and glycerol, was lower after copper ion supplementation compared with the control value. Interestingly, the NADPH/NADP ratio always exceeded 1.9 in the present study, suggesting that the reduced forms were dominant during the whole fermentation period. At 108 hr of culture, the NADPH/NADP ratio peaked and highest reduction power was obtained, mainly because glucose was almost completely consumed (Figure 3), and optimal NADPH amounts are needed for polyol synthesis. At the end of fermentation when the carbon source is exhausted, erythritol and glycerol are gradually consumed again. Figure 3 also presented the typical profiles of polyol production.
Viburnum opulus fruit extract-capped gold nanoparticles attenuated oxidative stress and acute inflammation in carrageenan-induced paw edema model
Published in Green Chemistry Letters and Reviews, 2022
Cristina Bidian, Gabriela Adriana Filip, Luminița David, Bianca Moldovan, Ioana Baldea, Diana Olteanu, Mara Filip, Pompei Bolfa, Monica Potara, Alina Mihaela Toader, Simona Clichici
In inflammation, polymorphonuclear neutrophils (PMNs) play an important role because of their migration in inflamed tissues, attraction to chemokines, and due to their ability to eliminate pathogens by degranulation, phagocytosis, neutrophil extracellular traps, and cytokine release (8). Endogenous reactive oxygen species (ROS), released by NADPH-oxidase activity regulate pathways dependent on tyrosine phosphorylation, control phagocytosis, and modulate the expression of cytokines and chemokines involved in the inflammatory response (9).
Production of lipid-containing microalgal biomass and simultaneous removal of nitrate and phosphate from synthetic wastewater
Published in Environmental Technology, 2018
M. S. V. Prasad, A. K. Varma, P. Kumari, P. Mondal
The variation in lipid content with inoculum concentration and time at constant nitrate concentration of 1.5 g L−1 is shown in Figure 3(a). It is observed that the maximum lipid content of 16.65% occurred after 27 days with 6% inoculum concentration. Every microorganism needs a specific time for cell division and metabolic activity. Microalgae require sufficient time to uptake different constituents of growth media as well as for their conversion to cell biomass through various metabolic pathways. So, lipid content can be increased by increasing the inoculum concentration and time. Many microalgae strains accumulate appreciable amount of lipids under the influence of stress conditions. Various studies reported that high lipid content follows low growth rate with simultaneous decrease in biomass productivity [24]. An increase in the lipid content is observed with a decrease in the nitrate concentration. This can be explained based on the well-known facts that, under nitrogen stress conditions, more metabolic flux is generated by photosynthesis and accumulation of large quantities of lipid takes place due to significant penetration of light at low cell density and to sustain adverse conditions [25]. Under a nitrogen starvation condition, lipid accumulation increases significantly; the possible reason could be that, under nitrogen deficiency condition, the available nitrogen is utilized for synthesis of enzyme and essential cell structures. Any carbon dioxide subsequently fixed is converted into carbohydrate or lipid rather than protein. Another possible reason could be that under nitrogen limitation condition, NADPH consumption is decreased due to unavailability of nitrogen pool, which blocks the amino acid synthesis pathways, especially the reaction from α-ketoglutarate to glutamate, thus resulting in accumulation of excess NADPH in the cells. For synthesis of fatty acids, NADPH acts as a reducing power and plays a very important role in the two steps of reduction process in the pathway of fatty acid biosynthesis. In order to accumulate lipid, metabolic activities in a cell require sufficient time. The effect of nitrate concentration and time at a constant inoculum concentration of 4.5% on lipid content is shown in Figure 3(b). Nitrogen limitation would cause three changes such as decrease in the cellular content of thylakoid membrane, activation of acyl hydrolase and stimulation of the phospholipid hydrolysis. These changes enhance the intracellular content of fatty acid acyl-CoA and activate diacylglycerol acyltransferase converting acyl-CoA into triglyceride (TAG) [26]. Thus, nitrogen stress conditions show enhancement in lipid and TAG content of microalgae cells. The results from Figure 3(c) show a decrease in lipid with an increase in the nitrate concentration. It is also clear that an increase in the inoculum concentration with a decrease in the nitrate concentration shows good lipid content. These results show effective interdependency of nitrate and inoculum concentration in growth medium with cellular lipid content.