Which of the following is NOT one of the key enzymes of gluconeogenesis?

Gluconeogenesis is the metabolic pathway that results in the generation of glucose from certain non-carbohydrate substrates. This pathway is crucial for maintaining blood glucose levels during fasting or intense exercise. Key enzymes in gluconeogenesis include pyruvate carboxylase, which converts pyruvate to oxaloacetate, fructose-1,6-bisphosphatase, which catalyzes the conversion of fructose-1,6-bisphosphate to fructose-6-phosphate, and PEPCK (phosphoenolpyruvate carboxykinase), which converts oxaloacetate to phosphoenolpyruvate.

In contrast, glycogen phosphorylase plays a different role in glucose metabolism; it is primarily involved in glycogenolysis, the process of breaking down glycogen into glucose-1-phosphate for energy use when the body requires immediate glucose supplies. Therefore, glycogen phosphorylase is not a key enzyme in gluconeogenesis, as it does not contribute to the synthesis of glucose from non-carbohydrate precursors. This distinction is essential for understanding how the body regulates glucose levels through various metabolic pathways.