Biochemistry

Phosphorylase (active) р р Moreover, phosphorylase catalyzes the cleavage of glucosyl residues to the branching point of the glycogen chain, then dextranase takes effect, which breaks the 1-6 bond of glycogen and provides further action of phosphorylase. Phosphorylase exists in two forms: inactive (b) and active (a). The conversion of phosphorylase b to phosphorylase a occurs with the participation of ATP, the enzyme phosphorylase kinase and c-AMP as a coenzyme. And from two molecules of inac ­ tive phosphorylase, one active is obtained. This process is stimulated by the hormones adrenaline and glucagon, which contribute to the formation of c-AMP (Fig. 11.2). The rate of the phosphorylase reaction depends on the concentration of glycogen, phosphoric acid and glucose-6-phosphate. With a decrease in the concentration of glycogen and phosphoric acid, the rale of this process decreases (Fig. 11.3). The released glucose- 1 -phosphate is converted into glucose-6-phosphate by the action of the enzyme of phosphoglucomutase. Glucose-6-phosphate is included in the processes of glycolysis or is converted into free glucose, which from the “ depot ” enters the blood and is used by the tissues as an energetic material (Fig. 11.4). / 4APP, Phosphotase phosphorylase 4ATP. 4H»0 Phosphcrylase Phosphorylase b (less active} i 3 H 2 О H Glucose-6-phosphatase Ң Figure 11.2 - Transformations of phosphorylases Thus, the constant concentration of glucose in the blood is the result of the simultaneous flow of two processes: the flow of glucose into the blood from the liver and its consumption from the blood by tissues in which glucose is used mainly as an energetic material. 218