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
Pyridoxal phosphate is required for 
Select and explain. 
A. Gluconeogenesis, B. Glycogenolysis, C. Glycolysis, D. Fatty acid oxidation
B: Glycogenolysis
Answer: B: Glycogenolysis 
Explanation: Glycogen phosphorylase removes glucose as glucose-1-phosphate from glycogen (phosphorolysis). It contains pyridoxal. Formation of branches in glycogen phosphate (PLP) as a prosthetic group. The alpha-1,4 linkages in the glycogen are cleaved. removes glucose units one at a time. Enzyme sequentially hydrolyses alpha-1,4 glycosidic linkages, till it reaches a glucose residue, 3-4 glucose units away from a branch point. It cannot attack the 1,6 linkage at branch point.Ref: DM Vasudevan, 7th edition, page no: 124