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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.
Enhancing the production of poly-γ-glutamate in Bacillus subtilis ZJS18 by the heat- and osmotic shock and its mechanism
Published in Preparative Biochemistry & Biotechnology, 2020
Yichao Song, Yishu Zhang, Min He, Hang Liu, Chunyu Hu, Liuzhen Yang, Ping Yu
As shown in Figure 3a, the activity of glucose-6-phosphate dehydrogenase under all three conditions was decreased with the fermentation time prolonged, indicating that the concentrations of the carbon sources and other nutrients decreased as the cells grew. This also made the concentration of enzyme-catalyzed substrate decreased, resulting in reducing the activity of enzyme. Glucose-6-phosphate dehydrogenase first participates in the pentose phosphate pathway in the endogenous glutamate metabolism. Its role is to catalyze the conversion of 6-phosphoglucose to 6-phosphogluconate. Glyceraldehyde-3-phosphate and fructose-6-phosphate are generated in the pentose phosphate pathway, and reentered the glycolysis pathway [24]. The activity of glucose-6-phosphate dehydrogenase was the highest under unshocked condition compared to the other two shock conditions (Figure 3a), which increased the metabolic rate of the pentose phosphate pathway and resulted in loss of carbon sources toward the biosynthesis of γ-PGA. Thus, it was speculated that heat- and osmotic shock could improve the biosynthesis of γ-PGA by decreasing the activity of glucose-6-phosphate dehydrogenase.