lecture_24legge - Gluconeogenesis Gluconeogenesis is the...

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11/13/2009 1 Gluconeogenesis / TCA 11/12/2009 Gluconeogenesis Gluconeogenesis is the process whereby precursors such as lactate, pyruvate, glycerol, and amino acids are converted to glucose. Fasting requires all the glucose to be synthesized from these non-carbohydrate precursors. Most precursors must enter the Krebs cycle at some point to be converted to oxaloacetate. Oxaloacetate is the starting material for gluconeogenesis Overview of Glucose Metabolism The metabolic fate of pyruvate Free energy changes in glycolysis Reaction enzyme Δ G ° ´ Δ G ° 1 Hexokinase -20.9 -27.2 2 PGI +2.2 -1.4 3 PFK -17.2 -25.9 4 Aldolase +22.8 -5.9 5 TIM +7.9 +4.4 6+7 GAPDH+PGK -16.7 -1.1 8 PGM +4.7 -0.6 9 Enolase -3.2 -2.4 10 PK -23.3 -13.9
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11/13/2009 2 Gluconeogenesis is not just the reverse of glycolysis Several steps are different so that control of one pathway does not inactivate the other. However many steps are the same. Three steps are different from glycolysis. 1 Pyruvate to PEP 2 Fructose 1,6- bisphosphate to Fructose-6- phosphate 3 Glucose-6-Phosphate to Glucose Gluconeogenesis versus Glycolysis Gluconeogenesis versus Glycolysis Pyruvate is converted to oxaloacetate before being changed to Phosphoenolpyruvate 1. Pyruvate carboxylase catalyses the ATP-driven formation of oxaloacetate from pyruvate and CO 2 2. PEP carboxykinase (PEPCK) concerts oxaloacetate to PEP that uses GTP as a phosphorylating agent.
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This note was uploaded on 02/22/2011 for the course BCHS 3304 taught by Professor Johnson during the Spring '08 term at University of Houston.

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lecture_24legge - Gluconeogenesis Gluconeogenesis is the...

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