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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].
The ROS/NF-κB/HK2 axis is involved in the arsenic-induced Warburg effect in human L-02 hepatocytes
Published in International Journal of Environmental Health Research, 2022
Fanshuo Yin, Ying Zhang, Xin Zhang, Meichen Zhang, Zaihong Zhang, Yunyi Yin, Haili Xu, Yanmei Yang, Yanhui Gao
It is known that arsenic at low concentrations contributes to cell proliferation and malignant transformation by activating certain signal pathways that are reported to be involved in regulating the Warburg effect (Presek et al. 1988; Medda et al. 2021). The nuclear factor kappa B (NF-κB) signaling pathway is one of these pathways (Xiong et al. 2020; Quiroga et al. 2021). This pathway, the most common dysfunctional signal pathway in human cancers, also plays a regulatory role in the Warburg effect by regulating the transcription of metabolic-related genes, such as hexokinase 2 (HK2) (Kooshki et al. 2021). NF-κB is a dimeric complex composed of five subunits, namely RelA (p65), RelB, c-Rel, NF-κB1 (p105/p50), and NF-κB2. The p65 subunit, as the main functional subunit, is involved in the function of the nuclear transcription factor (Hayden and Ghosh 2004, 2008). There is evidence that arsenic at low concentrations activates the NF-κB signaling pathway (Renu et al. 2020; Tang et al. 2021) and upregulates the HK2 protein, a key enzyme of glycolysis. It can therefore be hypothesized that the NF-κB signaling pathway may participate in the arsenic-induced Warburg effect by regulating the expression of HK2.
Optimizing secretory expression of recombinant human interferon gamma from Kluyveromyces lactis
Published in Preparative Biochemistry & Biotechnology, 2018
Rajat Pandey, Venkata Dasu Veeranki
At very high concentrations of substrate, K. lactis cells reorganize their metabolic pathways and starts utilizing ethanol and acetate as a carbon source to support its growth (Figure 8). Lactose and galactose transport systems in K. lactis have been studied in-depth and it has been shown that lactose uptake is either by active transport (Figure 9) or by simple diffusion process.[26] The transport system is under monogenic control and is inducible. As soon as lactose is taken up by K. lactis cells, β–galactosidase (EC: 3.2.1.23) degrades it into D-galactose and α D-glucose. Hexokinase (EC: 2.7.1.1) converts α D-glucose to α D- glucose 6P and it enters into glycolysis. D-galactose also follows the same fate of entering into glycolysis pathway but after a multistep process involving at least four enzymes; namely, (a) aldose 1-epimerase (EC: 5.1.3.3), (b) galactokinase (EC: 2.7.1.6), (c) UDPglucose-hexose-1-phosphate uridylyltransferase (EC: 2.7.7.12), (d) phosphoglucomutase (EC: 5.4.2.2).