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The Pentose Phosphates Pathway—Glucogenesis
Published in Jean-Louis Burgot, Thermodynamics in Bioenergetics, 2019
The enzyme catalyzing the reaction is the glucose-6-phosphate dehydrogenase. The lactone is hydrolyzed to the acid-6-phosphogluconate under the action of a specific lactonase (Figure 101): Structure of 6-phosphogluconate acid.Then, the 6-phosphogluconate acid undergoes oxidation and decarboxylation. The keto-pentose ribulose-5-phosphate is formed under the action of the enzyme 6-phosphogluconate dehydrogenase. It is interesting to notice that, then, there is formation of a second molecule of NADPH (Figure 102): 6-phosphogluconateacid→6-phosphogluconatedehydrogenaseD-ribulose-5-phosphateFormation of ribulose-5-phosphate.
Proteomics investigation of molecular mechanisms affected by EnBase culture system in anti-VEGF fab fragment producing E. coli BL21 (DE3)
Published in Preparative Biochemistry and Biotechnology, 2019
Bahareh Azarian, Amin Azimi, Mahboubeh Sepehri, Vahideh Samimi Fam, Faegheh Rezaie, Yeganeh Talebkhan, Vahid Khalaj, Fatemeh Davami
Ribose 5-phosphate isomerase A (RPIA) is up-regulated in EnBase cultured cells at the end of the increased growth rate phase. RPIA catalyzes the reversible conversion of ribulose 5-phosphate to ribose 5-phosphate as a step of non-oxidative branch of pentose phosphate pathway (PPP). PPP is the major source for production of NADPH which serves as a reducing power in anabolic pathways of amino acid and lipid biosynthesis.[25] In addition to the production of NADPH, the intermediates of PPP are precursors to biosynthesis of amino acid, nucleic acid, and lipopolysaccharides.[26–28] Increased activity of PPP due to RPIA up-regulation in EnBase cultured cells provides a capacity for higher metabolic and biosynthetic activities.
The effect of NADPH oxidase inhibitor diphenyleneiodonium (DPI) and glutathione (GSH) on Isatis cappadocica, under Arsenic (As) toxicity
Published in International Journal of Phytoremediation, 2021
Zahra Souri, Naser Karimi, Parvaiz Ahmad
Exposure to As triggers the overproduction of ROS thereby inducing the oxidative stress through stimulating the ROS-producing enzymes e.g., NADPH oxidases, and inhibiting the mechanisms involved in biosynthesis of molecules regulating the redox homeostasis (Flora 2011; Gupta et al.2013; Janků et al.2019; Mishra et al.2019). On the other hand, the main source of ROS involved and the mechanisms implicated in GSH mediated alleviation under As stress are broadly unexplored (Gupta et al.2013; Mishra et al.2019). During As toxicity, oxidative stress triggered through the overproduction of ROS and disturbances of antioxidative responses have been demonstrated as a key function in plant cells (Lin et al.2008; Sharma 2012; Gupta et al.2013). Greater activity of NADPH oxidase stimulates the production of O2− and H2O2 (Figure 8), and consequently oxidative stress that is suggested to be primarily responsible for oxidative toxicity (Figure 8). Due to disruption of cellular redox balance and NADPH/NADP+ ratio, the use of DPI as an inhibitor of NADPH oxidase disrupts many biochemical pathways dependent on NADP such as pentose phosphate pathway and consequently reducing the GSH levels (Figure 8). The pentose phosphate pathway produces ribulose 5-phosphate, a precursor to ribose and deoxy ribose required for RNA and DNA synthesis (Noctor et al.2006). Moreover, the oxidized glutathione (GSSG) is recovered by NADPH from the pentose phosphate pathway (Figure 8). It has also been reported that, NADPH is crucial for key antioxidative functions like GR activity, an important enzyme in the AsA-GSH cycle to protect the stress mediated oxidative stress (Gill et al.2013; Corpas and Barroso 2014). Optimal concentrations of GSH are required for several biochemical pathways and the recycling of GSSG and GSH form an essential factor for improving the chelating capacity in hyperaccumulator plants. Upon As exposure, GSH content drops as a consequence of its incorporation into PC biosynthesis and it has been noted that As is detoxified by complexation with PC and/or vacuolar sequestration (Karimi et al.2009; Guo et al.2012; Souri et al.2017).