Pyruvate dehydrogenase glycolysis

Net reaction for glycolysis, pyruvate dehydrogenase, and the citric acid cycle... 

Acetyl-CoA is a potent allosteric effector of glycolysis and gluconeogenesis. It allosterically inhibits pyruvate kinase (as noted in Chapter 19) and activates pyruvate carboxylase. Because it also allosterically inhibits pyruvate dehydrogenase (the enzymatic link between glycolysis and the TCA cycle), the cellular fate of pyruvate is strongly dependent on acetyl-CoA levels. A rise in... 

Glycolysis yields cytosolic pyruvate, which (after transport into the mitochondria) is converted to acetyl-CoA by pyruvate dehydrogenase. 

Figure 5.3 Major control points of glycolysis and the TCA cycle. Enzymes I, hexokinase II, phosphofructokinase III, pyruvate kinase IV, pyruvate dehydrogenase V, citrate synthase VI, aconitase VII, isocitrate dehydrogenase VIII, a-oxoglutarate dehydrogenase.

ATP-proton motive force interconversion Electron transport Entner-Doudoroff Fermentation Glycolysis/gluconeogenesis Pentose phosphate pathway Pyruvate dehydrogenase Sugars TCA cycle Methanogenesis Polysaccharides Other... 

Pyruvate formed by glycolysis is converted into acetyl-CoA pyruvate dehydrogenase also generates one NADH per pyruvate so the net gain is 2 x 3 ATP = 6 so far,... 

In the brain, when ketones are metabolized to acetyl CoA, pyruvate dehydrogenase is inhibited. Glycolysis and subsequently glucose uptake in brain decreases. This important switch spares body protein (which otherwise would be catabolized to form glucose by gluconeogenesis in the liver) by allowing the brain to indirectly metabolize fetty acids as ketone bodies. 

We know that anaerobic glycolysis of glncose yields pyruvate and/or lactate, interconvertable metabolites. Pyruvate is converted into acetyl-SCoAin the following reaction, catalyzed by the pyruvate dehydrogenase complex ... 

Figure 6.4 Glycolysis divided into five stages. It is not clear whether the reaction in which pyruvate is converted to acetyl-CoA, catalysed by pyruvate dehydrogenase, should be classified as a glycolytic enzyme or an enzyme of the Krebs cycle. Since the enzyme presents acetyl-CoA to the cycle, it is considered in this book as an enzyme of glycolysis (i.e. aerobic glycolysis).

Pyruvate, the product of glycolysis, is converted to acetyl-CoA, the starting material for the citric acid cycle, by the pyruvate dehydrogenase complex. 

TABLE 16-1 Stoichiometry of Coenzyme Reduction and ATP Formation in the Aerobic Oxidation of Glucose via Glycolysis, the Pyruvate Dehydrogenase Complex Reaction, the Citric Acid Cycle, and Oxidative Phosphorylation... 

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