Which enzyme catalyzes the rate-limiting step in glycogenolysis?

Glycogenolysis is the metabolic process through which glycogen is broken down into glucose molecules to be used for energy. The key enzyme that catalyzes the rate-limiting step of this process is glycogen phosphorylase. This enzyme cleaves glycogen into glucose-1-phosphate by adding inorganic phosphate (Pi) to the glycogen chain, effectively mobilizing glucose for energy production within the body.

Glycogen phosphorylase is regulated by various factors, including hormonal signals, which help control the energy needs of the body during fasting or physical activity. The regulation of this enzyme is crucial for maintaining blood glucose levels and ensuring the availability of glucose during periods of increased metabolic demand.

In contrast, the other enzymes listed do not play a direct role in glycogenolysis. Hexokinase is involved in the glycolytic pathway, converting glucose to glucose-6-phosphate, while phosphofructokinase regulates an earlier step in glycolysis. Fructose-1,6-bisphosphatase, on the other hand, is part of gluconeogenesis, which is the process of synthesizing glucose from non-carbohydrate precursors. These enzymes fulfill important metabolic roles but do not catalyze