Glucose metabolism and pathway diversityVoet, Fundamentals, 3rdFig. 16.1Pentose – phosphate – pathway (PPP)Voet, Fundamentals, 3rdFig. 15.35Pthhtth (PPP) b lPentose –phosphate –pathway (PPP) balanceComplete cycle:1 glucose-6-P + 12 NADP+ 6 CO2 + 12 NADPH + Pi Oxidative branch:6 glucose-6-P + 12 NADP+ 6 ribulose-5-P + 6 CO2 + 12 NADPHNon oxidative branch:Non oxidative branch:6 ribulose-5-P 5 glucose-6-P + PiThe pentose phosphate pathway.Oxidative branchNon-oxidative branchVoet, Fundamentals, 3rdFig. 15.30Step 1: The glucose-6-phosphate dehydrogenase reaction.The two reducing power (NADPH) generating steps inFig on page 522generating steps in the oxidative branchgpgStep 2: The phosphogluconate dehydrogenase reaction.Fig. 15.31Voet, Fundamentals, 3rdThe non-oxidative branch of the pentose phosphate cycle includes C5 + C5 C7 + C3 pentose phosphate cycle includes several interconversion steps of C7, C4, and C3 ketoses and aldoses as follows:C7 + C3 C4 + C6 C4+C5C6+C3C4 C5C6 C3Fig. Non-oxidative branch of Pentose Phosphate PathwayGlycogen synthesis and degradation (glucose storage and retrieval)Voet, Fundamentals, 3rdFig. 16.6The activation of G-1-P to UDP-glucoseFigure 16-7Voet, Fundamentals, 3rdFig. GTP is used to activate glucose-1-P in plant cells for the synthesis (ADP-glucose for starch in plants)ggpfyof cellulose.Fig. Glycogen degradation is activated by glucagon mediated phosphorylation of phosphorylase (a or active form) while the simultaneous phosphorylation )ppyof synthase causes this enzyme to be inactive (b form).Ch 20, Cox-LehningerThe control of glycogen phosphorylase activity.Voet, Fundamentals, 2ndFig. Full hormonal control of glycogen synthase in human skeletal muscle. Note that the phosphorylase shows reciprocal response to phosphorylation via ppy p pppycAMP mediated kinase activity (PKA). GPCR stands for G-Protein coupled receptor, a 7-transmembrane helix spanning protein.Voet, Fundamentals,
View Full Document