This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: All India exam, Subject name: Biochemistry
Allantoin is the end product of metabolism of ? 
Select and explain. 
A. Glycogen, B. Purine, C. Pyrimidine, D. Histidine
B: Purine
Answer: B: Purine 
Explanation: In non-primate mammals, end product of purine metabolism is allantoin due to presence of enzyme uricase. Uricase convees uric acid to allantoin. Humans lack the enzyme uricase. Therefore, end product of purine catabolism in humans is uric acid REF: Lippincott book of biochemistry 6th ed.