Bioenergetics
Michael H. Stone, Timothy J. Suchomel, W. Guy Hornsby, John P. Wagle, Aaron J. Cunanan in Strength and Conditioning in Sports, 2023
Beginning with one molecule of glucose, the net production of glycolysis is two molecules of ATP. However, starting with glycogen, which is broken down into Glucose-6-phospohate (G-3-P) via the enzyme phosphorylase, then three ATP are produced (Figure 2.3a). The additional ATP is produced as a result of the phosphorylation step that uses an ATP (via hexokinase) is bypassed and one ATP is spared. In comparing fast versus slow glycolysis and the fate of the two sarcoplasmically produced NADH2, it can be argued that the net ATP production for slow glycolysis can be as much as eight ATP when the process starts with glucose. This occurs as a result of the NADH2 entering the mitochondria and producing an additional 6 ATP through oxidative phosphorylation. It should be noted that there can be differences in ATP production between cardiac and skeletal muscle. Evidence indicates that two different shuttle systems operate to transfer electrons into the mitochondria, one in heart muscle (malate-aspartate) and the other in skeletal muscle (glycerol-phosphate) (226). In the glycerol-phosphate system, FAD picks up the NADH+ and carries it to the electron transport system, thus reducing the number of ATP being produced. Some evidence indicates that the glycerol-phosphate system predominates in type II muscle fibers, while type I fibers can also use the malate-aspartate system (128, 226).
Metabolism
Peter Kam, Ian Power, Michael J. Cousins, Philip J. Siddal in Principles of Physiology for the Anaesthetist, 2020
Electrons are transferred from NADH + H+ and FADH2 into the transport chain, which forms an energy gradient from high to low potential from beginning to end. As the electrons pass along the chain, down the gradient, they lose energy harnessed by the chain to form ATP at three specific points. The energy released from the electrons is used to pump hydrogen ions across the inner mitochondrial membrane to the cytoplasmic side, producing a very high hydrogen ion concentration locally. At three points along the electron transport chain, there are molecular pores across the inner membrane so that the hydrogen ions can flow down their concentration gradient back into the matrix. As they do so, energy is released and is used to produce ATP from ADP and phosphate ions. There are therefore three points on the chain where ATP can be formed. As NADH + H+ donates electrons at the beginning of the chain, three ATP molecules are formed. FADH2 donates electrons further down the chain and only produces two ATP molecules.
Cardiovascular Disease and Oxidative Stress
Peter Grunwald in Pharmaceutical Biocatalysis, 2019
The mitochondrial electron transport chain is involved in the transport of electrons and is embedded within the inner mito-chondrial membrane. It generates a proton gradient and regenerates electron carriers. Two specific carriers, NADH and FADH2, pass through the electron transport chain, releasing electrons through an oxidation reaction (Turrens, 2003). These electrons are used in catabolic processes to release energy in the form of ATP to the rest of the body (Stein and Imai, 2012). Both NADH and FADH2 are principally produced in the TCA cycle during cellular respiration, and NADH donates electrons in redox reactions when the electron energy is high (Murphy, 2009). Instead of donating, FADH2 feeds the electrons into the transport chain directly through the mitochondrial complex II (Quinlan et al., 2012). The mitochondrial electron chain is a transport for potential ROS to enter any biological system through exchanging, passing, and adding of electrons (Liemburg-Apers et al., 2015).
Role of oxidative stress in diabetes-induced complications and their management with antioxidants
Published in Archives of Physiology and Biochemistry, 2023
Hasandeep Singh, Rajanpreet Singh, Arshdeep Singh, Harshbir Singh, Gurpreet Singh, Sarabjit Kaur, Balbir Singh
The majority of glucose influx in cells is destined to produce fuel for the development of ATP through oxidative phosphorylation in the mitochondrial respiratory chain complex, which has been understood for decades (Kashihara et al. 2010). Once within the cell, glucose is converted to pyruvate, which is then metabolised in the Krebs cycle to produce nicotinamide (NADH) and flavin adenine dinucleotide (FADH2). These molecules act as electron donors during oxidative phosphorylation and produce adenosine triphosphate (ATP) in mitochondria (Sagoo and Gnudi 2018). In mitochondrial respiratory chain complexes I – IV, electrons from NADH or FADH2 are passed to molecular oxygen (O2) to produce ATP (Kashihara et al. 2010). Under normal physiological conditions, the majority of O2 is reduced to water, and less than 1% of O2 is converted to the superoxide anion O2−. However, there is surplus leakage of electrons at two main sites in mitochondrial dysfunctional or hyperglycaemic states, one at complex I and the other at the interface between coenzyme Q and complex III. Thus, the mitochondrial respiratory chain has been identified as the primary source of superoxide production in mammalian cells (Addabbo et al. 2009, Kowaltowski et al. 2009, Riemer et al. 2009, Skulachev et al. 2009). The mitochondrial capacity to transport electrons is overcome under conditions of hyperglycaemia (high glucose) and/or mitochondrial dysfunction, resulting in an increase in superoxide development (Nishikawa et al. 2000, Brownlee 2001, Chen et al. 2003).
A comprehensive proteomics analysis of the response of Pseudomonas aeruginosa to nanoceria cytotoxicity
Published in Nanotoxicology, 2023
Lidija Izrael Živković, Nico Hüttmann, Vanessa Susevski, Ana Medić, Vladimir Beškoski, Maxim V. Berezovski, Zoran Minić, Ljiljana Živković, Ivanka Karadžić
The upregulation of several enzymes involved in lipid catabolism through the β-oxidation of fatty acids were found: acetyl-CoA acetyltransferase, acyl-CoA dehydrogenase, acyl-CoA thiolase, and long-chain-fatty-acid-CoA ligase (Table 1), suggesting increased generation of acetyl-CoA, which enters the citric acid cycle, and NADH and FADH2 that are used for further oxidation and energy production. Interestingly, dihydrolipoyl dehydrogenase, which contains lipoamide as a cofactor, was downregulated, indicating reduced synthesis of lipid structures. Impaired structures and reduced biosynthesis of fatty acids and lipids in association with ROS that cause lipid peroxidation in P. aeruginosa produce a strong effect on maintaining bacterial cell integrity, primarily through the effects on membrane phospholipids, lipidated membrane proteins that are tightly connected to transport machinery, and lipopolysaccharides of the outer membrane, responsible for permeability. Notably, even the intact outer membrane of P. aeruginosa has low permeability to various compounds, not only toxic, but also nutritional substrates (Tamber, Ochs, and Hancock 2006).
Metalloproteinases and NAD(P)H-dependent oxidoreductase within of Bay nettle (Chrysaora chesapeakei) venom
Published in Toxin Reviews, 2022
Mayra Pamela Becerra-Amezcua, Mónica Alejandra Rincón-Guevara, Irma Hernández-Calderas, Xochitl Guzmán-García, Isabel Guerrero-Legarreta, Humberto González-Márquez
The protein of approx. 37 kDa is a NAD(P)/FAD-dependent oxidoreductase, although oxidoreductases have been detected in the jellyfish C. fuscescens (Ponce et al.2016), N. nomurai (Yue et al.2017b) and Cyanea sp. (Liang et al.2019), little is known about its effects. L-amino acid oxidases (LAAOs) had been found in venoms of snakes. These enzymes belong to the family called NAD(P)/FAD-dependent oxidoreductase that also comprises polyamine oxidase (PAO), flavin-containing monoamine oxidases (MAOs), D-amino acid dehydrogenase, and linoleic acid isomerase. Moreover, have various pathological and physiological activities, including induction of apoptosis, edema, platelet aggregation/inhibition, hemorrhagic, and anticoagulant activities (Ullah 2020). In general, the LAAOs are homodimers with molecular masses ranging from 120 to 150 kDa in their native form and 50 to 70 kDa in their monomeric forms (Costa et al.2014), but in jellyfish, homology with these enzymes has been found in proteins with smaller molecular weights (45–18 kDa) (Yue et al.2017b), which could indicate that in these organisms these enzymes are smaller.
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