This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Amino Acid Metabolism, Subject name: Biochemistry
In pyridoxine deficiency, tryptophan is converted to - 
Select and explain. 
A. Nicotine, B. Acetoacetate, C. Xantheurenic acid, D. Acetyl CoA
C: Xantheurenic acid
Answer: C: Xantheurenic acid 
Explanation: Ans. is 'c' i.e., Xantheurenic acid o In vitamin B6 deficiency the metabolism is shuted to xanthurenic acid. Therefore, xantheurenic acid excretion is increased in urine.