NANP Board Practice Exam

Which enzyme catalyzes glycogen degradation?

1. Amylase

2. Glycogen phosphorylase

3. Glycogen synthase

4. Lactase

The correct answer is: Glycogen phosphorylase

The enzyme that catalyzes glycogen degradation is indeed glycogen phosphorylase. This enzyme plays a critical role in the process of breaking down glycogen into glucose-1-phosphate, which can then be converted into glucose-6-phosphate and utilized for energy. Glycogen phosphorylase acts on the α(1→4) glycosidic bonds of glycogen, effectively mobilizing glucose for periods of fasting or energy demand. While amylase is involved in the digestion of carbohydrates by breaking down starch, it does not specifically degrade glycogen. Glycogen synthase is responsible for glycogen synthesis, working to build glycogen from glucose, contrary to the action of glycogen phosphorylase. Lactase, on the other hand, is involved in the digestion of lactose, the sugar found in milk, and has no role in glycogen metabolism. This context highlights the specific function of glycogen phosphorylase as integral in the process of glycogen mobilization.