This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Glycogen Metabolism and Glycogen Storage, Subject name: Biochemistry
McArdles disease is due to the deficiency of: 
Select and explain. 
A. Glucose 1 phosphatase, B. Glucose 1, 6 diphosphatase, C. Glucose 6 phosphatase, D. Myophosphorylase
D: Myophosphorylase
Answer: D: Myophosphorylase 
Explanation: Ans: D (Myophosphorylase) Ref: Harper's illustrated Biochemistry,28th edition,Chapter 19,pp 160Explanation:McArdles diseaseType V Glycogen storage diseaseDeficiency: muscle phosphorylase/myophosp- horylasePremature chain termination, incorrect folding etc can cause loss of catalytic activitySkeletal muscle is affectedExercise-induced muscular pain, cramps, progressive weakness, myoglobinuriaNo increase in blood lactate after exerciseGlycogen storage disordersDisorderAffected TissueEnzyme defectType 0LiverGlycogensynthaseType I; Von Gierke'sLiver, kidney, intestineGlucose-6-phosphataseType II; Pompe'sAilLysosomal alpha glucosidaseType III; Forbe'sLiver, muscle, heartGlycogendebranching enzymeType IV; Anderson'sLiverBranching enzymeType V; Mc Ardle'sMusclesmuscle phosphory laseType VI; Her'sLiverLiver phosphon/laseType VII; Tauri'sSkeletal muscle, RBCMuscle and Liver PFK