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: Physiology
Xanthinurate is a product/intermediate metabolite of 
Select and explain. 
A. Phenylalanine, B. Leucine, C. Tryptophan, D. Isoleucine
C: Tryptophan
Answer: C: Tryptophan 
Explanation: Conversion of tryptophan metabolite 3 hydroxy kynurenine to 2 hydroxy anthranilate is impaired in vitamin B6 deficiency? hence large amount of xanthinurate is formed.