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Construction of Enzyme Biosensors Based on a Commercial Glucose Sensor Platform
Published in Krzysztof Iniewski, Biological and Medical Sensor Technologies, 2017
Here, the developments of two types of ATP biosensors are described which are based on new combinations of enzymes and electrodes by using the coimmobilizations of HBH, G6PDH, and HEX on a Clark-type oxygen electrode and on a screen-printed electrode. The schematic illustrations for the biosensor setup and the determination principles are shown in Figure 6.4. HEX transfers the phosphate group from ATP to glucose to form glucose-6-phosphate. G6PDH catalyzes the specific dehydrogenation of glucose-6-phosphate by consuming NADP+. The product “NADPH” initiates the irreversible hydroxylation of p-hydroxybenzoate by HBH to consume dissolved oxygen and generate 3,4-dihydroxybenzoate. During the measurement of ATP, a detectable signal caused by the consumption of oxygen by HBH can be monitored at −0.6 V versus Ag/AgCl by the Clark-type electrode, and another detectable signal caused by the generation of 3,4-dihydroxybenzoate by HBH can be monitored at 0.42 V versus Ag/AgCl by the screen-printed electrode. The electronic signals are monitored and processed with a potentiostat, and the data acquisitions are performed with a computer.
Construction of Enzyme Biosensors Based on a Commercial Glucose Sensor Platform
Published in Šeila Selimovic, Nanopatterning and Nanoscale Devices for Biological Applications, 2017
Here, the development of two types of ATP biosensors are described, which are based on new combinations of enzymes and electrodes by using the coimmobilizations of HBH, glucose-6-phosphate dehydrogenase (G6PDH), and hexachlorocyclopentadiene (HEX) on a Clark-type oxygen electrode and on a screen-printed electrode. Schematic illustrations for the biosensors’ setup and their determination principles are shown in Figure 10.4. HEX transfers the phosphate group from ATP to glucose to form glucose-6-phosphate. G6PDH catalyzes the specific dehydrogenation of glucose-6-phosphate by consuming NAD(P)+. The product, NADPH, initiates the irreversible hydroxylation of p-hydroxybenzoate by HBH to consume dissolved oxygen and generate 3,4-dihydroxybenzoate. During the measurement of ATP, a detectable signal caused by the consumption of oxygen by HBH can be monitored at −0.6 V versus Ag/AgCl by the Clark-type electrode, and another detectable signal caused by the generation of 3,4-dihydroxybenzoate by HBH can be monitored at 0.42 V versus Ag/AgCl by the screen-printed electrode. These electronic signals are monitored and processed with a potentiostat, and the data acquisitions are performed using a computer.
Enzyme Catalysis
Published in Harvey W. Blanch, Douglas S. Clark, Biochemical Engineering, 1997
Harvey W. Blanch, Douglas S. Clark
As can be seen on Figure 3.17, the metabolism of both glucose and glutamine are interrelated; however, glutamine typically provides most of the energy required by the cell through respiration. In all mammalian cells, glucose is metabolized to pyruvate. In normal (i.e., non-tumor) cells, pyruvate is converted to acetyl-CoA and oxidized via the TCA cycle. The ATP produced by mitochondrial respiration regulates glycolysis as a result of its inhibition of phosphofructokinase (PFK). Glucose-6-phosphate then accumulates and regulates the phosphorylation of glucose via its action on hexokinase. When oxygen is less
Comparative assessment of blood glucose monitoring techniques: a review
Published in Journal of Medical Engineering & Technology, 2023
Nivad Ahmadian, Annamalai Manickavasagan, Amanat Ali
Hexokinase is a glycolytic enzyme that promotes the transition process of glucose to glucose-6-phosphate (G-6-P) by utilising the energy from adenosine triphosphate (ATP) that provides the phosphate group. In the presence of magnesium ions, glucose is converted to glucose-6-phosphate (G-6-P) and adenosine diphosphate (ADP) [17]. In the next stage, G-6-P oxidises nicotinamide adenine dinucleotide phosphate (NADP) to reach the reduced form (NADPH) [18]. The final substance is 6-phosphogluconic acid. The hexokinase-based glucose detection method utilises spectrophotometry (Figure 2). NADPH strongly absorbs a particular wavelength of ultraviolet (UV) light at 340 nm, which is the main target in the monitoring of the HK method [17,18]. NADPH’s absorption value directly relates to the glucose concentration level, making this method a standard laboratory technique [19]. The detection process is prolonged according to several enzyme reaction chains [17,18,20].
Role of key enzymes in the production of docosahexaenoic acid (DHA) by Thraustochytrium sp. T01
Published in Preparative Biochemistry & Biotechnology, 2023
D. Muthu, C. Kabilan, Sathyanarayana N. Gummadi, Anju Chadha
The glucose-6-phosphate dehydrogenase activity was assayed by measuring NADPH formation. 10 µg protein concentration of the cell-free extract was added to the reaction mix containing 34 mM tris-chloride buffer, 0.85 mM glucose-6-phosphate, and 6.8 mM magnesium chloride (MgCl2). The mix was made up to 1 ml by adding water. The reaction was initiated by adding 68 µM NADP+. The sample was then spectrophotometrically analyzed using UV-VIS spectroscopy (Jasco V530) for the rate of increase in absorbance at 340 nm. One unit (U) of enzyme activity is the amount of enzyme required to reduce 1 µmol of NADP+ per minute.[27]