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Environmental Health
Published in Lorris G. Cockerham, Barbara S. Shane, Basic Environmental Toxicology, 2019
Camille J. George, William J. George
Individual susceptibility to chemicals occurs in all species resulting in a different response in individuals exposed to the same concentration of chemical (Ottoboni, 1984). Unusual reactions to drugs may be inherited without the hereditary trait being directly associated with the metabolism or disposition of the drug. There are several inherited red blood cell enzymatic deficiencies which result in unusual adverse effects if certain drugs are given. The best known example is the variety of deficiencies of erythrocyte glucose-6-phosphate dehydrogenase (G6PD). The variants with <30% of the normal activity of the enzyme develop hemolytic reactions to primaquine and other drugs. The reduced level of G6PD results in a decreased production of NADPH, the reduced cofactor for glutathione reductase synthesis. An adequate supply of glutathione is critical for maintaining the integrity of the erythrocyte membrane. A variety of chemicals causes hemolysis in individuals deficient in G6PD. Males are more likely to show the deficiency and drug sensitivity than females since the gene responsible for G6PD is carried on the X chromosome (LaDu et al., 1971).
Construction of Enzyme Biosensors Based on a Commercial Glucose Sensor Platform
Published in Krzysztof Iniewski, Biological and Medical Sensor Technologies, 2017
Here, an amperometric biosensor for PGM activity with a bienzyme screen-printed biosensor is described. As shown in Figure 6.7, the principle is as follows: PGM (EC 5.4.2.2, from rabbit muscle, Sigma) converts glucose-1-phosphate to glucose-6-phosphate. Glucose-6-phosphate dehydrogenase (G6PDH, EC 1.1.1.49, from Leuconostoc mesenteroides, Sigma) catalyzes the specific dehydrogenation of glucose-6-phosphate by consuming NAD+. The product “NADH” initiates the irreversible decarboxylation and the hydroxylation of salicylate by salicylate hydroxylase (SHL, EC 1.14.13.1, from Pseudomonas sp., GDS Technology Inc., Elkhart, IN) in the presence of oxygen to produce catechol, which results in a detectable signal due to its oxidation at the working electrode.
Clinical Toxicology of Copper
Published in Debasis Bagchi, Manashi Bagchi, Metal Toxicology Handbook, 2020
Sonal Sekhar Miraj, Mahadev Rao
Cu works as a co-factor for the function of cellular enzymes, such as catalase, cytochrome oxidase, dopamine-beta-hydroxylase, and peroxidase. Cu toxicity usually affects in the order: erythrocytes, liver, and kidney. Excessive levels of Cu inhibit sulfhydryl groups on enzymes, such as glucose-6-phosphate (G6PD) and glutathione reductase, which protect cells from oxidative stress-induced damage by free radicals. Inhibition of G6PD causes hemolysis. Intravascular hemolysis happens within 12–24 h after the ingestion of copper sulfate. Cu ions can oxidize Fe to form methemoglobin, thereby oxygen-carrying capacity of blood declines. Clinically, this state is exhibited by cyanosis and chocolate brown blood. Acute Cu poisoning leads to erosion of the epithelial lining of the GI tract along with centrilobular necrosis of the liver and acute tubular necrosis (ATN) in the kidney. Cu produces direct damage to the proximal renal tubules, and ATN occurs following Cu poisoning without the appearance of hypotension or severe hemolysis (Dash 1989). Additionally, intravascular hemolysis plays a major role in the pathogenesis of renal failure. The heme pigment generated from hemolysis and direct toxicity of Cu released from lysis of red cells attribute to damage of tubular epithelium of both kidneys. Moreover, GI manifestations such as severe vomiting, diarrhea, lack of replacement of fluid and GI bleed, leading to hypotension, which could also contribute to renal failure. Renal complications can appear on the third or fourth day or onward following the poisoning. Copper sulfate, because of its corrosive nature, causes caustic burns of esophagus, superficial and deep ulcers in the stomach and the small bowel. Metallothionein is a cysteine-rich, low-molecular-weight protein that binds to Cu and provides some protection against Cu toxicity. The formation of metallothionein occurs early in acute Cu toxicity both in the liver as well as in the kidney (Kurisaki et al. 1988). Chronic Cu toxicity does not usually happen in humans due to transport systems, which regulate absorption as well as excretion (Turnlund et al. 2005). Cu toxicity is most likely to happen in people with the liver disorder or other disease conditions in which excretion of bile is compromised (Araya et al. 2006). Evidence shows that a link between chronic exposure to large concentrations of Cu and a decline in intelligence in young adolescence (Tamura and Turnlund 2004). Postpartum depression has also been linked with high levels of Cu, since Cu concentrations increase throughout pregnancy to almost double normal values, and it may take up to 3 months after delivery for Cu concentrations to normalize (Crayton and Walsh 2007).
Comparative proteomic analysis revealed the metabolic mechanism of excessive exopolysaccharide synthesis by Bacillus mucilaginosus under CaCO3 addition
Published in Preparative Biochemistry & Biotechnology, 2019
Hongyu Xu, Zhiwen Zhang, Hui Li, Yujie Yan, Jinsong Shi, Zhenghong Xu
Glucose-6-phosphate isomerase (Pgi), a second glycolytic enzyme, catalyzed the reversible aldose–ketose isomerization of glucose-6-phosphate to fructose 6-phosphate. This enzyme is also an enzymatic link between glycolysis and the pentose phosphate pathway.[27] 6-Phosphofructokinase (PfkA) was believed to be the most important element for the control of glycolytic flux. This enzyme catalyzes a physiologically reversible interconversion of fructose-6-phosphate and fructose-1,6-bisphosphate.[28] Aconitate hydratase (Acn), which transforms citrate to isocitrate, was the first step of the TCA cycle.[29] Glucose-6-phosphate dehydrogenase (G6PD) directed glucose-6-phosphate into the pentose phosphate pathway and played a pivotal role in cell function.[30] In this study, we found that all the four enzymes were down-regulated with CaCO3 addition and created a decreased carbon flux toward the growth of cells.
Antioxidant enzymes responses in shoots of arsenic hyperaccumulator, Isatis cappadocica Desv., under interaction of arsenate and phosphate
Published in Environmental Technology, 2018
Zahra Souri, Naser Karimi, Letúzia M. de Oliveira
Glutathione levels in plant tissues are known to clearly relate to oxidative pentose phosphate cycle. This is probably due to providing NADPH by oxidative pentose phosphate cycle for the GSH production [49]. Therefore, we studied the possible role of phosphorus on GR activity against toxicity by supplementing As-containing medium. The GR activity increased significantly (p < 0.05), with increasing P exposure (Figure 4(d)), paralleling results obtained with the P. vitata [50]. Enhanced P application in I. cappadocica may be attributed to enhanced GSH production. Based on Kong et al. [49] study, the oxidative pentose phosphate cycle was clearly connected with the GSH metabolism. In this shunt, Glucose-6-phosphate dehydrogenase (G6PDH) is the key enzyme for the oxidative pentose shunt, which provides the NADPH required for the activation of GR and GSH production [49]. Therefore, P had a positive effect on GR activity, which may be due to regulation of GSH biosynthesis within plants.