This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Metabolism of carbohydrate, Subject name: Biochemistry
Enzyme activated by covalent phosphorylation is 
Select and explain. 
A. Glycogen phosphorylase, B. Acetyl CoA carboxylase, C. HMG CoA reductase, D. Pyruvate carboxylase
A: Glycogen phosphorylase
Answer: A: Glycogen phosphorylase 
Explanation: Glycogen phosphorylase removes glucose as glucose-1-phosphate from glycogen(phosphorolysis). It contains pyridoxal phosphate as a prosthetic group.Ref: DM Vasudevan, 7th edition, page no: 124