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Nutritional Deficiencies
Published in Philip B. Gorelick, Fernando D. Testai, Graeme J. Hankey, Joanna M. Wardlaw, Hankey's Clinical Neurology, 2020
Deepa Bhupali, Fernando D. Testai
Thiamine is a cofactor for: Transketolase: This enzyme links glycolysis to the hexose monophosphate shunt (Figure 17.1). The hexose monophosphate shunt is required for the synthesis of: Pentoses (such as ribose phosphate): necessary for the synthesis of nucleotides.Nicotinamide adenine dinucleotide phosphate (NADP): necessary for the synthesis of fatty acids, steroids, and antioxidants.Pyruvate dehydrogenase E1: Pyruvate dehydrogenase is a complex formed by three enzymes (E1, E2, and E3). This complex links the glycolytic pathway with the Krebs cycle. E1 requires thiamine pyrophosphate as a cofactor.Alpha-ketoglutarate dehydrogenase: This enzyme participates in the Krebs' cycle and is involved in the conversion of alpha-ketoglutarate to succinyl-CoA. The deficiencies of this enzyme and E1 lead to decreased adenosine triphosphate (ATP) production and cellular dysfunction.
Metabolism
Published in Peter Kam, Ian Power, Michael J. Cousins, Philip J. Siddal, Principles of Physiology for the Anaesthetist, 2020
Peter Kam, Ian Power, Michael J. Cousins, Philip J. Siddal
Free fatty acid synthesis occurs mainly in the liver and adipose tissue. In the liver, the main precursor for fatty acid synthesis is endogenous glucose derived from glycogen, lactate and blood glucose. Pyruvate is the main source of acetyl CoA, and this process is enhanced by raised plasma insulin concentration and lowered glucagon concentration. Acetyl CoA is an important substrate for the synthesis of free fatty acids under the control of acetyl-CoA-carboxylase. The acetyl CoA is converted first to malonyl CoA and then to fatty acid. Citrate formed in the citric acid cycle diffuses out of the mitochondrion and splits into acetyl CoA and oxaloacetate in the cytoplasm (Figure 65.16). The NADPH required for free fatty acid synthesis is supplied by the hexose monophosphate shunt and by the conversion of citrate to pyruvate in the cytoplasm. The hexose monophosphate shunt is highly active in the cytoplasm of the liver and adipose tissue.
Phagocytosis By Human Neutrophils
Published in Hans H. Gadebusch, Phagocytes and Cellular Immunity, 2020
Such an enzyme has been identified in human neutrophils237 but not well characterized, and its importance to the cell is unknown. A second possible mechanism for coupling NADH oxidation to the stimulation of the hexose monophosphate shunt involves the enzyme, NAD kinase, described in human neutrophils by DeChatelet et al.238 This enzyme catalyzes the following reaction:
Ulva lactuca methanolic extract improves oxidative stress-related male infertility induced in experimental animals
Published in Archives of Physiology and Biochemistry, 2021
Doaa A. Ghareeb, Alshimaa Abd-Elgwad, Nihal El-Guindy, Galila Yacout, Hala H. Zaatout
Gossypol injection significantly increased spermatozoa GSH level that may be considered as a defence mechanism against the oxidative damage which happened in testis. du Plessis et al. (2010) reported that increasing the ROS level have been correlated with decrease in sperm motility and this is consistent with our result where gossypol injection significantly increased the OS in seminal plasma and spermatozoa by increasing TBARS level. However, the exact mechanism through which ROS causes decreased motility is not understood. Thus, many hypotheses have been proposed to explain the link between ROS and decreased motility. One hypothesis shows that H2O2 can diffuse across the membranes into the cells and inhibit the activity of some vital enzymes such as G6PD. G6PD is an enzyme that controls the rate of glucose flux via the hexose monophosphate shunt and in turn, controlling the intracellular availability of NADPH. This is used as a source of electrons by spermatozoa to fuel the generation of ROS by an enzyme system known as NADPH oxidase (Villegas et al.2003).
Modulatory effect of isopulegol on hepatic key enzymes of glucose metabolism in high-fat diet/streptozotocin-induced diabetic rats
Published in Archives of Physiology and Biochemistry, 2021
Karunanithi Kalaivani, Chandrasekaran Sankaranarayanan
Liver is an important organ and plays a major role in maintaining glucose homeostasis by regulating glucose utilization and production. Hexokinase is one of the important key glycolytic and insulin sensitive enzymes (Vats et al. 2003). It catalyses the phosphorylation of glucose to glucose 6-phosphate, thereby channelizing glucose through the glycolytic pathway. The activity of hexokinase was decreased in diabetic rats leading to decreased glucose removal from blood. Pentose phosphate pathway (hexose monophosphate shunt) is an alternative route for the oxidation of glucose (Zhang et al. 2000). This pathway is found in the cytosol is responsible for the biosynthesis of NADPH and ribose-bi-phosphate. NADPH is required for the biosynthesis of glutathione, a non-enzymatic antioxidant. The activity of G6PDH, a rate limiting enzyme of this pathway is greatly decreased in diabetic rats. Administration of isopulegol at the effective dose of 100 mg/kg b.w. increased these enzyme activities thereby improving glucose utilization and oxidation. Our results are in line with Kurup et al. who reported that Averrhoa bilimbi ameliorated glycolytic enzymes in STZ-induced diabetic rats (Kurup and SM 2017).
Preclinical developments of enzyme-loaded red blood cells
Published in Expert Opinion on Drug Delivery, 2021
Luigia Rossi, Francesca Pierigè, Alessandro Bregalda, Mauro Magnani
Alcohol oxidase (AlOx) from Pichia pastoris (a methylotrophic yeast) has a much higher affinity for methanol than for ethanol. Based on this observation, we investigate the potential use of this enzyme for the treatment of methanol intoxication [77]. In fact, in humans, methanol is metabolized to formaldehyde by alcohol dehydrogenase and formaldehyde is metabolized to formic acid by acetaldehyde dehydrogenase, leading to cytochrome C oxidase inhibition. AlOx was encapsulated into human and murine erythrocytes up to 2 units/ml of packed cells. Enzyme‐loaded erythrocytes showed an increased rate of the hexose‐monophosphate‐shunt activity and a significant methemoglobin production resulting from the intracellular generation of H2O2. However, the in vivo survival of these cells did not seem to be significantly affected by methanol catabolism. In vivo, mice receiving AlOx‐loaded erythrocytes were able to keep the blood methanol concentrations below values that were about 50% of those found in control mice who received similar amounts of methanol. Thus, AlOx‐loaded erythrocytes may add an important contribution to the detoxification protocol against methanol poisoning. Formic acid can eventually be further degraded by encapsulate formate dehydrogenase [78].