Regulation and Integration of Metabolism-2008

Regulation and Integration ofMetabolism

Figure 12.16Activation of glycogen phosphorylase and inactivation of glycogen synthase. Phosphorylation reactions catalyzed by protein kinase A increase glycogen degradation. A green background indicates activated enzymes; a red background indicates inactivated enzymes. Green arrows signify activation; red arrows signify inactivation.Figure 12.17Activation of glycogen synthase and inactivation of glycogen phosphorylase. Hydrolysis of phosphate monoester bonds catalyzed by protein phosphatase-1 increases glycogen synthesis.Figure 12.18Regulation of glycogen metabolism by glucose in the liver. Inhibition of protein phosphatase-1 by glycogen phosphorylase a is relieved when glucose binds to the phosphorylase. Glycogen phosphorylase is then inactivated, and glycogen synthase is activated.Figure 16.24Triacylglycerol degradation in adipocytes. Epinephrine initiates the activation of protein kinase A, which catalyzes the phosphorylation and activation of hormone-sensitive lipase. The lipase catalyzes the hydrolysis of triacylglycerols to monoacylglycerols and free fatty acids. The hydrolysis of monoacylglycerols is catalyzed by monoacylglycerol lipase.