Question

Malignant hyperthermia is a genetic abnormality in which exposure to certain agents, especially the widely used general anes. thetic halothane, produces a dramatic rise in body temperature, acidosis, hyperkalemia, and muscle rigidity. Death is rapid if the condition is untreated and may occur the first cime a susceptible person is anacstictiad. The defect causes an inappropriate release of \(\mathrm{Ca}^{2+}\) from the sarcoplasmic reticulum of muscle. Many heat-producing processes are stimulated in an uncontrolled fashion by the release of \(\mathrm{Ca}^{2+}\), including glycolysis and glycogenolysis. Thosphorylation-dephosphorylation and allosteric accivation of enzymes play roles in stimularing glycogen degradation. All of the following result in enzyme activation except A. phosphorylation of phosphorylase kinase. B. binding of AMP to phosphorylase b. C. phosphorylation of phosphorylase. D. phosphorylation of protein kinase \(A\). E. dephosphorylation of glycogen synchase.

Short answer

A. Phosphorylation of phosphorylase kinase B. Binding of AMP to phosphorylase b C. Phosphorylation of phosphorylase D. Phosphorylation of protein kinase A E. Dephosphorylation of glycogen synthase Answer: E. Dephosphorylation of glycogen synthase

Step-by-step solution

A. Phosphorylation of phosphorylase kinase

The phosphorylation of phosphorylase kinase activates it. When phosphorylase kinase is active, it can phosphorylate glycogen phosphorylase to stimulate glycogen degradation.

B. Binding of AMP to phosphorylase b

Phosphorylase b becomes allosterically activated by AMP binding. In this state, it stimulates glycogen degradation as well.

C. Phosphorylation of phosphorylase

The phosphorylation of glycogen phosphorylase converts it to its active form, stimulating glycogen degradation.

D. Phosphorylation of protein kinase A

Protein kinase A, when phosphorylated, becomes active and further participates in the activation of phosphorylase kinase, which then leads to glycogen degradation.

E. Dephosphorylation of glycogen synthase

Dephosphorylation of glycogen synthase actually inactivates the enzyme rather than activating it. Glycogen synthase is involved in glycogen synthesis, which is the opposite of glycogen degradation. Thus, dephosphorylation of this enzyme results in reduced glycogen synthesis, rather than stimulating its degradation. Based on the analysis, the correct answer is: E. Dephosphorylation of glycogen synthase.