This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Biochemistry
Which one of the following coenzyme is associated with glycogen phosphorylase? 
Select and explain. 
A. Thiamine pyrophosphate, B. Tetrahydrofolate, C. Flavin mononuleotide, D. Pyridoxal phosphate
D: Pyridoxal phosphate
Answer: D: Pyridoxal phosphate 
Explanation: Glycogen phosphorylase has a pyridoxal phosphate (PLP, derived from Vitamin B6) at each catalytic site. Pyridoxal phosphate links with basic residues and covalently forms a Schiff base. Once the Schiff base linkage is formed, holding the PLP molecule in the active site, the phosphate group on the PLP readily donates a proton to an inorganic phosphate molecule, allowing the inorganic phosphate to in turn be deprotonated by the oxygen forming the a-1,4 glycosidic linkage.